U.S. patent application number 14/099589 was filed with the patent office on 2014-04-03 for back-off retry with priority routing.
This patent application is currently assigned to LSI Corporation. The applicant listed for this patent is LSI Corporation. Invention is credited to Jeffrey J. Gauvin, Stephen B. Johnson, Christopher McCarty, William K. Petty.
Application Number | 20140095754 14/099589 |
Document ID | / |
Family ID | 43974993 |
Filed Date | 2014-04-03 |
United States Patent
Application |
20140095754 |
Kind Code |
A1 |
Johnson; Stephen B. ; et
al. |
April 3, 2014 |
Back-Off Retry with Priority Routing
Abstract
A method for back-off retry with priority routing includes
routing a data transfer between an input of a single, cohesive SAS
expander and an output of the SAS expander via at least one
inter-expander link (IEL), the expander including a first SAS
expander and at least one additional SAS expander. The method
includes routing a first OPEN request on a direct path through the
first SAS expander to a port of a device and routing a second OPEN
request on an alternate path from the first SAS expander and
through a second SAS expander to the port of the device. The method
further includes, upon determination of a failed link or a busy
link, re-routing the data transfer from the second SAS expander to
the first SAS expander or a third SAS expander, or retrying the
data transfer through the second SAS expander.
Inventors: |
Johnson; Stephen B.;
(Colorado Springs, CO) ; McCarty; Christopher;
(Colorado Springs, CO) ; Petty; William K.;
(Colorado Springs, CO) ; Gauvin; Jeffrey J.;
(Manitou Springs, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LSI Corporation |
San Jose |
CA |
US |
|
|
Assignee: |
LSI Corporation
San Jose
CA
|
Family ID: |
43974993 |
Appl. No.: |
14/099589 |
Filed: |
December 6, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13008706 |
Jan 18, 2011 |
8656058 |
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14099589 |
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12384291 |
Apr 2, 2009 |
8077605 |
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13008706 |
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12384287 |
Apr 2, 2009 |
7913023 |
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12384291 |
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12384288 |
Apr 2, 2009 |
8321596 |
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12384287 |
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12791244 |
Jun 1, 2010 |
8244948 |
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12384288 |
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12384289 |
Apr 2, 2009 |
7849248 |
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12791244 |
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61191037 |
Sep 5, 2008 |
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61191037 |
Sep 5, 2008 |
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61191037 |
Sep 5, 2008 |
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61191037 |
Sep 5, 2008 |
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Current U.S.
Class: |
710/300 |
Current CPC
Class: |
G06F 11/2017 20130101;
H04L 45/28 20130101; G06F 13/4022 20130101; H04L 45/22 20130101;
G06F 11/2007 20130101 |
Class at
Publication: |
710/300 |
International
Class: |
G06F 13/40 20060101
G06F013/40 |
Claims
1. A method for back-off retry in a single, cohesive serial
attached small computer system interface (SAS) expander,
comprising: routing a data transfer between an input of a single,
cohesive SAS expander and an output of the single, cohesive SAS
expander, wherein the single, cohesive expander includes a first
SAS expander, and at least one additional SAS expander, wherein the
first SAS expander is connected to the at least one additional SAS
expander via at least one inter-expander link (IEL) for
inter-expander communications, wherein the routing the data
transfer further includes: routing a first OPEN request on a direct
path through the first SAS expander to a port of a device; and
routing a second OPEN request on an indirect alternate path from
the first SAS expander and through a second SAS expander to the
port of the device, the indirect alternate path established via an
IEL connecting at least one phys of the first SAS expander for
inter-expander communications to at least one phys of the second
SAS expander for inter-expander communications; determining link
availability between the second SAS expander and the port of the
device; and upon determination of at least one of a failed link and
a busy link on the second SAS expander, re-routing the data
transfer from the second SAS expander to at least one of the first
SAS expander and a third SAS expander, or retrying the data
transfer through the second SAS expander.
2. The method of claim 1, wherein the IEL between the first SAS
expander and the at least one additional SAS expander connects the
first SAS expander to the at least one additional SAS expander via
at least one phy for inter-expander communications of the first SAS
expander and at least one phy for inter-expander communications of
the at least one additional SAS expander.
3. The method of claim 1, further comprising: sending a vendor
unique status SAS PRIMITIVE from the second SAS expander to the
first SAS expander upon determination that the second SAS is unable
to complete the data transfer to the port of the device.
4. The method of claim 1, wherein the determining link availability
between the second SAS expander and the port of the device
comprises: receiving an SAS PRIMITIVE status sent by the second SAS
expander, the SAS PRIMITIVE status received by the first SAS
expander.
5. The method of claim 1, wherein at least one of the failed link
and the busy link results from at least one of a physical
malfunction and a logical malfunction.
6. The method of claim 1, wherein the re-routing the data transfer
from the second SAS expander to at least one of the first SAS
expander and a third SAS expander comprises: re-routing the data
transfer from the second SAS expander to at least one of the first
SAS expander via an IEL path connecting at least one phys of the
first SAS expander for inter-expander communications to at least
one phys of the second SAS expander for inter-expander
communications and re-routing the data transfer from the second SAS
expander to a third SAS expander via an IEL path connecting at
least one phys of the second SAS expander for inter-expander
communications to at least one phys of the third SAS expander for
inter-expander communications.
7. The method of claim 1, wherein the retrying the data transfer
through the second SAS expander comprises: retrying the data
transfer through the second SAS expander via a functional link
between the second SAS expander and the port of the device.
8. The method of claim 1, wherein the inter-expander communications
utilize a SAS Management Protocol.
9. The method of claim 1, wherein the first SAS expander and the at
least one additional SAS expander each implement firmware
configured to operate the first SAS expander and the at least one
additional SAS expander as a single, cohesive expander.
10. The method of claim 1, wherein the port of the device
comprises: a wide port of the device.
11. The method of claim 1, wherein the re-routing the data transfer
from the second SAS expander to at least one of the first SAS
expander and a third SAS expander, or retrying the data transfer
through the second SAS expander comprises: repeatedly attempting to
re-route the data transfer from the second SAS expander to at least
one of the first SAS expander and a third SAS expander or retrying
the data transfer through the second SAS expander until a phy
suitable for completing the data transfer to the port of the device
becomes available.
12. The method of claim 1, wherein the re-routing the data transfer
from the second SAS expander to at least one of the first SAS
expander and a third SAS expander, or retrying the data transfer
through the second SAS expander comprises: repeatedly attempting to
re-route the data transfer from the second SAS expander to at least
one of the first SAS expander and a third SAS expander or retrying
the data transfer through the second SAS expander until a timeout
occurs.
13. A method for back-off retry in a single, cohesive serial
attached small computer system interface (SAS) expander,
comprising: routing a data transfer between an input of a single,
cohesive SAS expander and an output of the single, cohesive SAS
expander, wherein the single, cohesive expander includes a first
SAS expander, and at least one additional SAS expander, wherein the
first SAS expander is connected to the at least one additional SAS
expander via at least one inter-expander link (IEL) for
inter-expander communications; determining link availability
between the first SAS expander and a port of a device; upon
determination of at least one of a failed link and a busy link
between the first SAS expander and the port of the device,
re-routing the data transfer of the first SAS expander to a second
SAS expander on an indirect alternate path via an IEL path
connecting at least one phys of the first SAS expander for
inter-expander communications to at least one phys of the second
SAS expander for inter-expander communications; determining link
availability between the second SAS expander and the port of the
device; and upon determination of at least one of a failed link and
a busy link between the second SAS expander and the port of the
device, re-routing the data transfer from the second SAS expander
to at least one of the first SAS expander and a third SAS expander,
or retrying the data transfer through the second SAS expander.
14. The method of claim 13, wherein the IEL between the first SAS
expander and the at least one additional SAS expander connects the
first SAS expander to the at least one additional SAS expander via
at least one phy for inter-expander communications of the first SAS
expander and at least one phy for inter-expander communications of
the at least one additional SAS expander.
15. The method of claim 13, further comprising: sending a vendor
unique status SAS PRIMITIVE from the second SAS expander to the
first SAS expander upon determination that the second SAS is unable
to complete the data transfer to the selected connector of the
device.
16. The method of claim 13, wherein the determining link
availability between the second SAS expander and the port of the
device comprises: receiving an SAS PRIMITIVE status sent by the
second SAS expander, the SAS PRIMITIVE status received by the first
SAS expander.
17. The method of claim 13, wherein the re-routing the data
transfer from the second SAS expander to at least one of the first
SAS expander and a third SAS expander comprises: re-routing the
data transfer from the second SAS expander to at least one of the
first SAS expander via an IEL path connecting at least one phys of
the first SAS expander for inter-expander communications to at
least one phys of the second SAS expander for inter-expander
communications and re-routing the data transfer from the second SAS
expander to a third SAS expander via an IEL path connecting at
least one phys of the second SAS expander for inter-expander
communications to at least one phys of the third SAS expander for
inter-expander communications.
18. The method of claim 13, wherein the retrying the data transfer
through the second SAS expander comprises: retrying the data
transfer through the second SAS expander via a functional link
between the second SAS expander and the port of the device.
19. The method of claim 13, wherein the port of the device
comprises: a wide port of the device.
20. The method of claim 13, wherein the re-routing the data
transfer from the second SAS expander to at least one of the first
SAS expander and a third SAS expander, or retrying the data
transfer through the second SAS expander comprises: repeatedly
attempting to re-route the data transfer from the second SAS
expander to at least one of the first SAS expander and a third SAS
expander or retrying the data transfer through the second SAS
expander until a phy suitable for completing the data transfer to
the selected connector of the device becomes available.
21. The method of claim 13, wherein the re-routing the data
transfer from the second SAS expander to at least one of the first
SAS expander and a third SAS expander, or retrying the data
transfer through the second SAS expander comprises: repeatedly
attempting to re-route the data transfer from the second SAS
expander to at least one of the first SAS expander and a third SAS
expander or retrying the data transfer through the second SAS
expander until a timeout occurs.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority from the following
copending U.S. patent applications and is a continuation of U.S.
patent application Ser. No. 13/008,706, entitled "BACK-OFF RETRY
WITH PRIORITY ROUTING," filed Jan. 18, 2011, which is a
continuation-in-part of U.S. patent application Ser. No. 12/384,291
entitled, "METHOD FOR PROVIDING PATH FAILOVER FOR MULTIPLE SAS
EXPANDERS OPERATING AS A SINGLE SAS EXPANDER", filed Apr. 2, 2009,
now issued as U.S. Pat. No. 8,077,605; U.S. patent application Ser.
No. 12/384,287 entitled, "SPECIFYING LANES FOR SAS WIDE PORT
CONNECTIONS", filed Apr. 2, 2009, now issued as U.S. Pat. No.
7,913,023; U.S. patent application Ser. No. 12/384,288 entitled,
"SAS PAIRED SUBTRACTIVE ROUTING", filed Apr. 2, 2009, now issued as
U.S. Pat. No. 8,321,596; and U.S. patent application Ser. No.
12/791,244 entitled, "ALLEVIATING BLOCKING CASES IN A SAS SWITCH",
filed Jun. 1, 2010, now issued as U.S. Pat. No. 8,244,948.
[0002] Additionally, U.S. patent application Ser. No. 12/791,244
entitled, "ALLEVIATING BLOCKING CASES IN A SAS SWITCH", filed Jun.
1, 2010, claims priority from and is a continuation-in-part of U.S.
patent application Ser. No. 12/384,289 entitled, "COMBINING
MULTIPLE SAS EXPANDERS TO PROVIDE SINGLE SAS EXPANDER
FUNCTIONALITY", filed Apr. 2, 2009, now issued as U.S. Pat. No.
7,849,248.
[0003] Further, U.S. patent application Ser. No. 12/384,289
entitled, "COMBINING MULTIPLE SAS EXPANDERS TO PROVIDE SINGLE SAS
EXPANDER FUNCTIONALITY," filed Apr. 2, 2009; U.S. patent
application Ser. No. 12/384,291 entitled, "METHOD FOR PROVIDING
PATH FAILOVER FOR MULTIPLE SAS EXPANDERS OPERATING AS A SINGLE SAS
EXPANDER", filed Apr. 2, 2009; U.S. patent application Ser. No.
12/384,287 entitled, "SPECIFYING LANES FOR SAS WIDE PORT
CONNECTIONS", filed Apr. 2, 2009; and U.S. patent application Ser.
No. 12/384,288 entitled, "SAS PAIRED SUBTRACTIVE ROUTING", filed
Apr. 2, 2009 claim the benefit under 35 U.S.C. .sctn.119(e) of U.S.
Provisional Application Ser. No. 61/191,037, filed Sep. 5,
2008.
[0004] In addition, the present application incorporates by
reference all of the above applications.
TECHNICAL FIELD
[0005] The present disclosure generally relates to the field of
Serial Attached SCSI (SAS), and more particularly to a back-off
retry process implemented in a single, cohesive SAS expander
context.
BACKGROUND
[0006] Serial Attached SCSI (SAS) is a term referring to various
technologies designed to implement data transfer between computer
devices. The SAS protocol is a serial successor to the parallel
Small Computer System Interface. In the SAS protocol, all SAS
devices are either an initiator device, a target device, or an
expander device. Initiator devices are devices that begin an SAS
data transfer, while target devices are the devices to which
initiator devices transfer data. Together, initiator devices and
target devices are known as end devices.
[0007] SAS expanders are devices that facilitate data transfer
between multiple initiator devices and multiple target devices. The
SAS protocol utilizes a point-to-point bus topology. Therefore, if
an initiator device is required to connect to multiple target
devices, a direct connection must be made between the initiator
device and each individual target device in order to facilitate
each individual data transfer between the initiator device and each
individual target device. SAS expanders manage the connections and
data transfer between multiple initiator devices and multiple
target devices. SAS expanders may contain SAS devices.
SUMMARY
[0008] In one aspect, a method for back-off retry in a single,
cohesive SAS expander may include, but is not limited to, routing a
data transfer between an input of a single, cohesive SAS expander
and an output of the single, cohesive SAS expander, wherein the
single, cohesive expander includes a first SAS expander, and at
least one additional SAS expander, wherein the first SAS expander
is connected to the at least one additional SAS expander via at
least one inter-expander link (IEL) for inter-expander
communications, determining link availability between the first SAS
expander and a port of a device, then, upon determination of a
failed link or a busy link between the first SAS expander and the
port of the device, re-routing the data transfer of the first SAS
expander to a second SAS expander. The method further includes
determining link availability between the second SAS expander and
the port of the device, and, upon determination of a failed link or
a busy link between the second SAS expander and the port of the
device, re-routing the data transfer from the second SAS expander
to the first SAS expander or a third SAS expander, or retrying the
data transfer through the second SAS expander.
[0009] In another aspect, a method for back-off retry with priority
routing in a single, cohesive expander may include, but is not
limited to, routing a data transfer between an input of a single,
cohesive SAS expander and an output of the single, cohesive SAS
expander. The routing of data further includes routing a first OPEN
request on a direct path through a first SAS expander to a port of
a device while routing a second OPEN request on an alternate path
from the first SAS expander and through a second SAS expander to
the port of the device. The method further includes determining
link availability between the second SAS expander and the port of
the device, and, upon determination of a failed link or a busy
link, re-routing the data transfer from the second SAS expander to
the first SAS expander or a third SAS expander, or retrying the
data transfer through the second SAS expander.
[0010] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are not necessarily restrictive of the
present disclosure. The accompanying drawings, which are
incorporated in and constitute a part of the specification,
illustrate subject matter of the disclosure. Together, the
descriptions and the drawings serve to explain the principles of
the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The numerous advantages of the disclosure may be better
understood by those skilled in the art by reference to the
accompanying figures in which:
[0012] FIG. 1 is a block diagram illustrating a SAS topology
illustrating a single, cohesive SAS expander;
[0013] FIGS. 2A through 2E are block diagrams illustrating various
configurations of a single, cohesive SAS expander;
[0014] FIG. 3 is block diagram illustrating a blade center switch
configuration of a single, cohesive SAS expander;
[0015] FIG. 4 is a block diagram illustrating the inter-expander
links of a single, cohesive SAS expander;
[0016] FIG. 5 is a block diagram illustrating a failed internal
link within a single, cohesive SAS expander;
[0017] FIG. 6 is a flow diagram illustrating a method for combining
multiple SAS expanders to operate as a single, cohesive SAS
expander;
[0018] FIG. 7 is a flow diagram illustrating a method for providing
path failover when a link fails within a single, cohesive SAS
expander
[0019] FIG. 8 is a block diagram illustrating selecting lanes of
SAS wide ports for a data connection with a single, cohesive SAS
expander;
[0020] FIG. 9 is a flow diagram illustrating a method for
specifying lanes of SAS wide ports for a data connection with a
single, cohesive SAS expander.
[0021] FIG. 10A is a block diagram illustrating phy blocking
resulting from a lack of priority routing;
[0022] FIG. 10B is a block diagram illustrating a method for
priority routing;
[0023] FIG. 11A is a block diagram illustrating a method for
back-off retry;
[0024] FIG. 11B is a block diagram illustrating a method for
back-off retry with priority routing;
[0025] FIG. 11C is a block diagram illustrating a method for
back-off retry with priority routing; and
[0026] FIG. 12 is a flow diagram illustrating a method for back-off
retry with priority routing in a single, cohesive SAS expander
system.
[0027] FIG. 13 is a flow diagram illustrating a method for back-off
retry in a single, cohesive SAS expander system.
DETAILED DESCRIPTION
[0028] Reference will now be made in detail to the subject matter
disclosed, which is illustrated in the accompanying drawings.
[0029] A SAS topology featuring a single, cohesive SAS expander in
accordance with an exemplary embodiment of the present disclosure
is shown. The topology 100 may include initiator 110 connected to
expander 120 via narrow ports 115a . . . d. Expander 120 may be
connected to single, cohesive SAS expander 200 via narrow ports
125a . . . d. Single, cohesive SAS expander 200 may contain a
plurality of physically separate SAS expanders 202a . . . d. SAS
expanders 202a . . . d may be configured to share an identical SAS
address to combine narrow ports 125a . . . d to behave as single
common wide port 150. As shown in SAS topology 100, narrow ports
125a . . . d may combine to make x4-wide port 150. SAS expanders
202a . . . d may be connected to expander 130 via narrow ports 135a
. . . d. Expander 130 may be connected to target 140 via narrow
ports 145a . . . d. SAS specifications require that all connections
be point-to-point. However, SAS topology 100 is SAS specification
compliant because wide port 150 is a true SAS wide port.
[0030] Referring to FIGS. 2A-2E, cohesive SAS expander 200 may
contain a plurality of physically separated SAS expanders 202a . .
. h. SAS expanders 202a . . . h may be connected to output ports
205-244 via links 255a . . . h-294a . . . h. Widely varying
configurations of single, cohesive SAS expander 200 are
contemplated by the present disclosure, depending on the number of
SAS expanders 202a . . . h, the number of ports of SAS expanders
202a . . . h, the number of output ports 205-244, the width of
output ports 205-244, and the number of SAS expander ports used in
links 255a . . . h-294a . . . h.
[0031] Output ports 205-244 may be wide ports. Output ports 205-244
may be configured to share an identical SAS address. Under SAS
specifications, this defines output ports 205-244 to be a single
wide port of the same expander. Each of output ports 205-244 may be
connected to every SAS expander 202a . . . h (Not shown). The width
of output ports 205-244 may depend on how many SAS expander ports
are used in links 255a . . . h-294a . . . h to connect to each of
output ports 205-244. Each of SAS expander 202a . . . h may have
multiple SAS expander ports connected to each of output ports
205-244. For example, if single, cohesive SAS expander 200 contains
two SAS expanders 202a-h connected to each of output ports 205-244
via links 255a . . . h-294a . . . h using one SAS expander port,
then output ports 205-244 will be a x2 wide port. Furthermore, if
single, cohesive SAS expander 200 contains two SAS expanders 202a-h
connected to each of output ports 205-244 via links 255a . . .
h-294a . . . h using two SAS expander ports, then output ports
205-244 will be a x4 wide port. These configurations may allow for
simultaneous access of any port to any other port of single,
cohesive SAS expander 200 at full port bandwidth.
[0032] A blade center switch configuration 301 of single, cohesive
SAS expander 300 is provided. Referring to FIG. 3, multiple CPU
blades 302 may be connected to input ports 305-320. Input ports
305-320 may be wide ports. Input ports 305-320 may be configured to
share an identical SAS address. Under SAS specifications, this
defines input ports 305-320 to be a single wide port of the same
expander. Each of input ports 305-320 may be connected to each of
SAS expanders 202a . . . b via links 355a . . . b-375a . . . b (Not
shown). As shown in blade center switch configuration 301, input
ports 305-320 are x2 wide ports connected to two SAS expanders 202a
. . . b via links 355a . . . b-375a . . . b using one SAS expander
port, but other configurations are fully contemplated by these
disclosures. Each of SAS expanders 202a . . . b may be connected to
each of output ports 205-218 via links 255a . . . b-268a . . . b
(Not shown). As shown in blade center switch configuration 301,
output ports 205-218 are x4 wide ports connected to two SAS
expanders 202a . . . b via links 255a . . . b-268a . . . b using
two SAS expander ports, but other configurations are fully
contemplated by the current disclosure. Output ports 205-218 may be
connected to multiple data storage devices 303.
[0033] SAS expanders 202a . . . h may be configured to share an
identical SAS address. Under SAS specifications, this defines SAS
expanders 202a . . . h to be a single expander. Firmware may run on
each of SAS expanders 202a . . . h so SAS expanders 202a . . . h
behave and respond as a single expander. As shown in FIG. 4, each
of SAS expanders 202a . . . h may be connected to each of 202a . .
. h via inter-expander links (IEL) 430-435. IEL 430-435 may allow
SAS expanders 202a . . . h to communicate and coordinate to behave
and respond as a single expander. IEL 430-435 may communicate via
the SAS Management Protocol (SMP) or other communication methods,
such as Inter-Integrated Circuit Bus Protocol (I2C), Enhanced
Parallel Port (EPP), Ethernet, shared memory, and the like. IEL
430-435 may permit the IEL domain 420 to be zoned from primary
switched domain 410. Broadcasts may be disabled in IEL 430-435 to
eliminate any SAS specification non-compliant loop issues. IEL
430-435 may use multiple SAS expander ports. The phys used in IEL
430-435 may be completely hidden from the primary switched domain.
The numbering of the phys used in the primary switched domain of
SAS expanders 202a . . . h may be remapped to a single, logical
numbering. IEL 430-435 may allow any combination of SAS expanders
202a . . . h to fail while connectivity is maintained between any
functional SAS expanders 202a . . . h. Further, all input ports
305-320 and output ports 205-244 may maintain connectivity at a
reduced bandwidth in the event of less than every SAS expander 202a
. . . h failing. SMP target processing may be handled by a single
master SAS expander of single, cohesive SAS expander 200.
Connection requests to single, cohesive SAS expander 200 may be
routed to the single master SAS expander via IEL 430-435. SAS
expanders 202a . . . h may share SMP target processing.
[0034] Referring generally to FIG. 6, a method for combining
multiple SAS expanders is shown. For example, the method may
implement techniques for connecting and combining SAS expanders as
described below (and as shown in FIGS. 1, 2A through 2E, 3, and 4).
The method 600 may include the step of grouping at least one first
numbered phy of a first SAS expander with at least one second
numbered phy of a second SAS expander physically separate from the
first SAS expander into at least one common SAS wide port 602. For
example, the grouping into at least one common SAS wide port
(205-244) may include assigning an identical SAS address to the at
least one common wide port (205-244).
[0035] The method 600 may further include the step of assigning an
identical SAS address to the first SAS expander and the second SAS
expander 604. Assigning an identical SAS address to the first SAS
expander and the second SAS expander may allow the first SAS
expander and the second SAS expander to behave and respond as a
single, cohesive SAS expander 200. The assigning may be performed
via firmware executing on the first SAS expander and the second SAS
expander. Further, the phy numbering of the first SAS expander and
the second SAS expander may be remapped to appear as a single,
logically ordered phy numbering of a single, cohesive SAS expander.
For example, a first numbered phy of the first SAS expander may be
remapped to be in a first range of the single, logically ordered
numbering and a second numbered phy of the second SAS expander may
be remapped to be in a second range of the single, logically
ordered numbering.
[0036] The method 600 may further include the step of connecting
the first SAS expander directly to the second SAS expander for
inter-expander communications 606. The inter-expander
communications may utilize SMP communications or other
communication methods, such as Inter-Integrated Circuit Bus
Protocol (I2C), Enhanced Parallel Port (EPP), Ethernet, shared
memory, and the like. In additional embodiments, the connection
between the first SAS expander and the second SAS for
inter-expander communications (430-435) may be performed via the
phys of the first SAS expander and the phys of the second SAS
expander. Further, the phys of the first SAS expander for
inter-expander communications and the phys of the second SAS
expander for inter-expander communications may be hidden from the
primary switched domain (410) of the single, cohesive SAS expander.
At least two phys of the first SAS expander and at least two phys
of the second SAS expander may be used for inter-expander
communications between the first SAS expander and the second SAS
expander. Further, if at least one SAS expander within the single,
cohesive SAS expander remains operational (e.g., such as during an
SAS expander failure), all common SAS wide ports remain
operational, with all common SAS wide ports operating at a reduced
bandwidth.
[0037] The single, cohesive SAS expander 500 may be configured to
provide path failover when an internal link fails within the
single, cohesive SAS expander. Referring to FIG. 5, and as
described above, input ports 502-508 may be connected to each SAS
expanders 202a . . . d via links 552a . . . d-558a . . . d.
Further, input ports 502-508 may be SAS wide ports. Output ports
510-516 may be connected to each SAS expanders 202a . . . d via
links 560a . . . d-566a . . . d. Further, output ports 510-516 may
be SAS wide ports. Each of SAS expanders 202a . . . d may be
connected to each other via SAS expander ports for inter-expander
communications. As shown in single, cohesive SAS expander 500, the
link 566b between SAS expander 202c and output port 516 may fail.
For example, a physical defect may cause link 566b to fail. As a
further example, link 566b may fail to due a logical problem.
[0038] The data transfer intended to be transmitted via failed link
566b may be re-routed to another SAS expander connected to output
port 516. This data transfer may be re-routed to another SAS
expander via the phys used for inter-expander communications
between the SAS expanders. As shown in single, cohesive SAS
expander 500, the data transfer between SAS expander 202c and
output port 516 via failed link 566b may be re-routed through SAS
expander 202d via inter-expander communications link 434. From SAS
expander 202d, the data transfer may be re-routed to output port
516 via link 566c. Thus output port 516 may receive the data
transfer as originally intended, but may receive the data transfer
on a different phy. Further, if SAS expander 202d already has an
active link to output port 516, SAS expander 202c may respond to
the SAS initiator with an arbitration in progress (AIP), as
provided via SMP. The SAS initiator may attempt the data transfer
at a later time after receiving an AIP or OPEN REJECT (RETRY) SMP
response from SAS expander 202c.
[0039] In a further aspect of the present disclosure, firmware
executing on the SAS expanders may reprogram the SAS expander route
tables to re-route connections through inter-expander
communications links (430-435) instead of through the failed links.
Further, a SAS initiator connected to the single, cohesive SAS
expander may learn that link 566b has failed by receiving a CHANGE
primitive. For example, SMP provides a CHANGE primitive. The SAS
initiator may then perform a SAS Discovery, for example, as
provided via SMP. Further, the SAS initiator may note the number of
remaining active connections to the target, and may only initiate a
number of simultaneous data transfers equal to the number of
remaining active connections to the target.
[0040] Referring generally to FIG. 7, a method for providing path
failover while combining multiple SAS expanders to act as a single,
cohesive SAS expander is shown. For example, the method may
implement techniques as shown in FIG. 5. In one embodiment of the
current invention, the method 700 includes the step of detecting a
failed link between a first SAS expander and a device 702. For
example, the detected failed link may fail due to a physical
problem. The detected failed link may fail due to a logical
problem.
[0041] The method 700 may further include the step of re-routing a
data transfer of the first SAS expander connected to the device via
the failed link to a second SAS expander connected to the device
via a functional link 704. For example, the failed link of the
single, cohesive SAS expander may fail due to a physical problem
within the failed link. In another example, the failed link may
fail due to a logical problem. The first SAS expander may be
connected to the second SAS expander via the phys of the first SAS
expander and the phys of the second SAS expander for inter-expander
communications. In further embodiments, the re-routing a data
transfer of a SAS expander connected to a device via the failed
link to a second SAS expander connected to the device via the
functional link may occur via the phys of the first expander for
inter-expander communications and the phys of the second SAS
expander for inter-expander communications. In exemplary
embodiments, the re-routing a data transfer may include
reprogramming a route table of the first SAS expander to re-route
the data transfer from the failed internal link to the links
between via the phys of the first expander for inter-expander
communications and the phys of the second SAS expander for
inter-expander communications. For example, the reprogramming of
the route table of the first SAS expander may be performed via
firmware executing on the first SAS expander.
[0042] The step of re-routing data transfers from a failed link
within the single, cohesive SAS expander to a second SAS expander
via a link for inter-expander communications may not indicate to
SAS initiators and SAS targets connected to the single, cohesive
SAS expander that such re-routing is occurring. However, if the
second SAS expander currently has an active link to the device and
data is re-routed from the failed link to the second SAS expander,
the first SAS expander connected to the device via the failed link
may respond with an AIP response. In such a case, a SAS initiator
receiving the AIP response may retry the data transfer at a later
time. A SAS initiator connected to the single, cohesive SAS
expander may be notified of the failed link via receiving a CHANGE
primitive. Upon receiving a CHANGE primitive, the SAS initiator may
perform a SAS Discovery. For example, SMP provides a SAS Discovery,
which includes a SAS Discover and a SAS Discover response.
[0043] A SAS-initiator specified data connection configuration 800
is provided. Referring to FIG. 8, SAS initiator 810 may be
connected to SAS expander 820 via SAS wide port 880. At least one
phy of SAS expander 830 and at least one phy of SAS 840 may be
combined in common SAS wide port 890. In order for SAS expander 830
and SAS expander 840 to operate as a single, cohesive SAS expander,
SAS expander 830 may share an identical SAS address with SAS
expander 840. SAS expander 820 may be connected to SAS expander 830
and SAS expander 840 via common SAS wide port 890. SAS expander 830
may also be directly connected to SAS expander 840 via an
inter-expander communications link via the phys of SAS expander 830
and the phys of SAS expander 840. SAS expander 830 and SAS expander
840 may not operate as a single, cohesive SAS expander, and may be
in a cascaded configuration. A plurality of SAS targets 850-875 may
be connected to SAS expander 830 and SAS expander 840 via a SAS
narrow port. The number of SAS targets 850-875 may be greater than
the number of phys on SAS expander 830 or SAS expander 840. For
example, SAS targets 850-875 may be a hard disk array such as a
Just a Bunch Of Disks (JBOD) SAS array.
[0044] SAS initiator 810 may specify the lanes of wide ports 880,
890 to be used to create a data connection from SAS initiator 810
to one of SAS targets 850-875. Specifying the lanes of wide ports
880, 890, may be used for fairness control, where some lanes of
wide ports 880, 890 may be used to access SAS targets 850-875 and
other lanes of wide ports 880, 890 may be used to pass through to
other parts of a SAS configuration. SAS initiator 810 may further
specify the lanes within an OPEN frame of a connection request.
Such an OPEN frame may be provided via an SMP connection request.
SAS initiator 810 may have learned the optimal lanes for a data
connection from SAS initiator 810 to one of SAS targets 850-875 via
a performing a standard SAS discovery process. SAS expander 830 and
SAS expander 840, along with SAS targets 850-875 may be configured
to respond via the SMP Discover response with the optimal lanes for
a data connection from SAS initiator 810 to one of SAS targets
850-875. Each SAS expander in the data connection between SAS
initiator 810 and one of SAS targets 850-875 may check the OPEN
frame of the connection request from SAS initiator 810 for the
allowed lanes for the data connection and only makes a data
connection on those specified lanes.
[0045] Referring generally to FIG. 9, a method for specifying
allowable lanes of a SAS wide port for a data connection between a
SAS initiator and a SAS target in a SAS domain in accordance with
an exemplary embodiment of the present disclosure is shown. In a
current embodiment of the present disclosure, method 900 includes
the step of discovering the optimal lanes of at least one SAS wide
port for the data connection 902. For example, SAS initiator 810
may discover the optimal lanes for the data connection via
performing a standard SAS discovery process. Further, the SMP
Discover response may be used to communicate the optimal lanes for
the data connection to SAS initiator 810.
[0046] The method 900 may further include the step of specifying
the allowable lanes for the data connection within the SAS wide
ports of each level of the SAS domain 904. For example, the
allowable lanes for the data connection may be specified via a SAS
initiator connection request. The allowable lanes for the data
connection may further be specified within an OPEN frame of a SAS
initiator connection request.
[0047] The method 900 may further include the step of checking for
the specified allowable lanes for the data connection 906. For
example, when a SAS expander (820-840) receives an OPEN frame of a
SAS initiator connection request, the SAS expander may check the
OPEN frame for the specified allowable lanes for the data
connection.
[0048] The method 900 may further include the step of creating the
data connection of the specified allowable lanes 908. For example,
a SAS expander may create the data connection on the specified
allowable lanes. Further, the SAS expander may create the data
connection after checking the OPEN frame of a SAS initiator
connection request for the specified allowable lanes.
[0049] Referring generally to FIGS. 10A and 10B, the single,
cohesive SAS expander 1000 may be configured to provide priority
routing to limit blocking within the single, cohesive expander
1000. As previously described herein, the input ports 502-508 may
be connected to each of the SAS expanders 202a . . . d via links
552a . . . d-558a . . . d. Further, input ports 502-508 may be SAS
wide ports. Output ports 510-516 may be connected to each SAS
expanders 202a . . . d via links 560a . . . d-566a . . . d.
Further, output ports 510-516 may be SAS wide ports. It is
recognized that without providing a connection between the
individual SAS expanders 202a . . . d via the IEL paths (e.g.,
430-435) a blocking condition may occur in the single, cohesive
expander 1000 when OPEN requests are sent by initiators on two or
more connectors through one of the individual expanders 202a . . .
d of the single, cohesive expander 1000. In order to limit this
blocking condition, each of SAS expanders 202a . . . d may be
connected to each other via SAS expander ports for inter-expander
communications.
[0050] As illustrated in FIG. 10A, it is recognized that without
priority routing a blocking condition may also occur in the single,
cohesive expander 1000 when two or more OPEN requests are sent by
initiators on an input port through two or more of the individual
expanders 202a . . . d of the single, cohesive expander 1000. For
example, blocking may occur when an initiator on input port 502
sends an OPEN request from phy 0 of the input port 502 through
expander 202a intended for output port 510 and an initiator on
input port 502 sends an OPEN request from phy 1 of the input port
502 through expander 202b intended for output port 510. Without
priority routing, an expander, such as 202a, may employ a round
robin arbitration method to select a phy of the unused phys
available for routing to the selected designation. Without priority
routing, the expander 202a would then, in some instances, route the
single OPEN request along the indirect path 1002, wherein the OPEN
request is routed along the IEL path 430 to the second expander
202b.
[0051] As a result, if the expander 202a selects the IEL path 430
after being presented with only a single OPEN request from input
port 502 blocking may occur on the second expander 202b. More
specifically, if the second expander 202b is also routing an OPEN
request from an initiator of input port 502 to output port 510, as
illustrated by path 1004, the first expander 202a will be unable to
establish an indirect path to output port 510 via the second
expander 202b, as illustrated by the "X" on IEL path 430.
[0052] As illustrated in FIG. 10B, the blocking described in the
preceding description may be avoided by implementing a priority
routing scheme in the single, cohesive expander 1000. A priority
routing scheme may include, first, routing a first OPEN request
along a direct path (e.g., 1006) through an expander, and, second,
routing a second OPEN request along an alternate path (e.g., 1008)
from a first expander to a second expander via an IEL path.
[0053] In one embodiment, priority routing may include routing a
first OPEN request by an initiator of an input port 502-508 along a
direct path through an expander 202a . . . 202d to a designated
output port 510 . . . 516. For example, a first OPEN request by an
initiator on input port 502 may be routed by a first expander 202a
on a direct path 1006 to phy 0 of output port 510, while a second
OPEN request by an initiator on input port 504 may be routed by the
first expander 202a on an alternate path 1008 via the IEL path 430
connecting the first expander 202a and a second expander 202b. The
second expander 202b may then route the second request to phy 1 of
output port 510. By utilizing the alternate path 1008 only when an
expander receives a second OPEN request and always routing a first
OPEN request along the direct path 1006, the overall single,
cohesive expander 1000 may avoid or limit unnecessary phy
blocking.
[0054] It should be recognized that while the above description
describes the concept of priority routing in the context of
expanders 202a and 202b, input port 502 and input port 504, phy 0
and phy 1 of input port 502, and phy 0 and phy 1 of output port 510
this concept can readily and logically be extended to all of the
remaining expanders, input ports, output ports, and phys of the
presently described invention as the above description does not
represent a limitation but merely an illustration.
[0055] Referring generally to FIG. 11A, the single, cohesive SAS
expander 1100 may be configured to provide back-off retry when a
link within the single, cohesive expander 1100 fails or is busy. As
previously described herein, the input ports 502-508 may be
connected to each of the SAS expanders 202a . . . d via links 552a
. . . d-558a . . . d. Further, input ports 502-508 may be SAS wide
ports. Output ports 510-516 may be connected to each SAS expanders
202a . . . d via links 560a . . . d-566a . . . d. Further, output
ports 510-516 may be SAS wide ports. Moreover, each of SAS
expanders 202a . . . d may be connected to each other via SAS
expander ports for inter-expander communications.
[0056] It is recognized that the data transfer re-routing from a
first SAS expander 202a to an additional SAS expander (e.g., 202b,
202c or 202d) via the IEL paths 430 . . . 435 described previously
herein may result in a routing lock on the additional expander used
for re-routing. For example, upon determining a failed 560a link
(e.g., logical failure or physical failure) to the output port 510,
the data transfer intended to be transmitted via link 560a may be
re-routed from the first SAS expander 202a to a second SAS expander
202b via the IEL path 430, which couples the phys for
inter-expander communications of the first SAS expander 202a and
the phys for the inter-expander communications of the second
expander 202b. Provided the second SAS expander 202b has available
phys to re-route the data transfer and establish a link to another
phys of the original destination output port 510, the data transfer
may successfully be re-routed to the original destination output
port 510. However, in the event the second SAS expander 202b does
not have available phys to complete the re-routing of the data
transfer to the original destination output port 510, the single,
cohesive expander 1000 may experience phy blocking as the
re-routing process locks the connection to the second SAS expander
202b and the data transfer cannot be completed until the second
expander 202b obtains available phys to establish the link to the
output port 510.
[0057] As illustrated in FIG. 11A, a back-off retry process may be
implemented to limit the phy blocking described above. For example,
upon determining a failed 560a link to the output port 510, the
data transfer intended to be transmitted via link 560a may be
re-routed from the first SAS expander 202a to a second SAS expander
202b via the IEL path 430, which couples the phys for
inter-expander communications of the first SAS expander 202a and
the phys for the inter-expander communications of the second
expander 202b.
[0058] In the event the second SAS expander 202b does not have
available phys to complete the re-routing of the data transfer to
the original destination output port 510, the data transfer may be
re-routed back to the first SAS expander 202a or the data transfer
may be retried on the second expander 202b in the event a
functional link between 202b and output port 510 becomes available.
The first connection to complete on either the first expander 202a
or the second expander 202b will be used to complete the connection
to the destination output port 510. It is further recognized that
attempts to re-route the data transfer back to the first SAS
expander 202a or retry the data transfer on the second SAS expander
202b may be repeated until a phy suitable for completing the data
transfer to the output port 510 becomes available or the process
times out. As a result, no re-route locking occurs on the second
expander 202b.
[0059] It is further recognized that the back-off retry process may
be extended to more than two SAS expanders of the single, cohesive
expander 1100. For example, upon determining the second expander
202b cannot complete the connection to the output port 510, the
data transfer may be re-routed to a third SAS expander (e.g., third
SAS expander 202c or fourth SAS expander 202d), in addition to the
re-routing of the data transfer back to the first SAS expander 202a
above.
[0060] In a further aspect, the second SAS expander 202b (i.e., the
IEL receiving SAS expander) may reject the OPEN request re-routed
from the first SAS expander 202a (i.e., the sending SAS expander)
to the second SAS expander 202b when it does not have available
phys to complete the connection. Moreover, the second SAS expander
202b may indicate the presence of phy blocking by sending a vendor
unique status "SAS PRIMITIVE" back to the first SAS expander 202a.
Upon receiving the blocked connection SAS PRIMITIVE status, the
first expander 202a may re-route the connection to another
connection (e.g., first SAS expander 202a or a third SAS expander,
such as 202c or 202d) or retry the connection on the second SAS
expander 202b. This process may be repeated until a phy on one of
the expanders becomes available, allowing the first connection to
complete on either of the expanders to be used to complete the
connection to the destination output port 510.
[0061] Referring generally to FIGS. 11B and 11C, the single,
cohesive SAS expander 1100 may be configured to provide back-off
retry with priority routing in order to limit or eliminate phy
blocking in the single, cohesive expander 1100. As previously
described herein, the single, cohesive expander 1100 may provide a
priority routing scheme wherein a first OPEN request is always
routed on a direct path 1012 through an expander, and a second OPEN
request is routed along an alternate path 1014 from a first
expander 202a to a second expander 202b via an IEL path 430. It is
contemplated herein, as shown in FIG. 11B, that the priority scheme
may be combined with the back-off retry process in order to provide
simultaneous priority routing with back-off retry.
[0062] In one embodiment, a first OPEN request by an initiator on
input port 502 may be routed on a direct path 1012 by a first
expander 202a to the destination output port 510. Moreover, a
second OPEN by an initiator on input port 504 may be routed by the
first expander 202a on an alternate path 1014 via the IEL 430 to
the second expander 202b. In the event the second expander 202b
does not have available phy to complete the connection to the
original destination output port 510, a back-off retry process may
be implemented. For example, upon determining link 560b connecting
the second expander 202b to the output port 510 has failed, the
data transfer intended to be transmitted via link 560b may be
re-routed from the second SAS expander 202a back to the first SAS
expander 202a or the data transfer may be retried on the second
expander 202b. Again, as illustrated by the pair of arrows on IEL
430, the first connection to complete on either the first expander
202a or the second expander 202b will be used to complete the
connection to the destination output port 510.
[0063] In another embodiment, illustrated in FIG. 11C, the back-off
retry with priority routing process described above may be extended
generally to include more than two SAS expanders. Similarly to the
embodiment described above, a first OPEN request by an initiator on
input port 502 may be routed on a direct path 1012 by a first
expander 202a to the destination output port 510, while a second
OPEN request by an initiator on input port 504 may be routed by the
first expander 202 on an alternate path 1016 via the IEL 430 to the
second expander 202b. Upon determining the link 560b connecting the
second expander 202b to the output port 510 has failed or is busy,
the data transfer intended to be transmitted via link 560b may be
re-routed from the second SAS expander 202b back to the first SAS
expander 202a or to a third SAS expander (e.g., expander 202c or
expander 202d), or the data transfer may be retried on the second
expander 202b until a connection is completed. In the case of the
third SAS expander 202c, the data transfer intended to be
transmitted via link 560b may be re-routed from the second SAS
expander 202b to the third SAS expander 202c, as illustrated by
path 1018, or retried on the second SAS expander 202b until a
connection is completed. As illustrated by the pair of arrows on
IEL 433, the first connection to complete on either the second
expander 202b or the third expander 202b will be used to complete
the connection to the destination output port 510. In accordance
with FIG. 11c, it should be recognized that the data transfer may
be successively re-routed to all available SAS expanders connected
to the second SAS expander 202b or retried on expander 202b
repeatedly until a connection may be completed to output port
510.
[0064] Referring generally to FIG. 12, a method 1200 for back-off
retry with priority routing in a single, cohesive SAS expander is
illustrated in accordance with the present disclosure. In a first
step 1202, the method 1200 for back-off retry in a single, cohesive
SAS expander 1100 includes routing a data transfer between an input
(e.g., input ports 502 . . . 508) of a single, cohesive SAS
expander 1100 and an output (e.g., output ports 510 . . . 516) of
the single, cohesive SAS expander 1100. The single, cohesive
expander 1100 includes a first SAS expander 202a, and at least one
additional SAS expander (e.g., 202b . . . 202d), wherein the first
SAS expander 202a is connected to the at least one additional SAS
expander via at least one inter-expander link (IEL) (e.g. 430 . . .
435).
[0065] The routing step 1202 further includes an additional second
step 1204. The second step 1204 includes routing a first OPEN
request on a direct path 1012 through the first SAS expander 202a
to a port (e.g., output port 510) of the device. For example, a
first OPEN request by an initiator on input port 502 may be routed
by a first expander 202a on a direct path 1012 to an output port
510 of a device.
[0066] In addition, the routing step 1202 further includes a third
step 1206. The third step 1206 includes routing a second OPEN
request on an alternate path (e.g., 1014 or 1016) from the first
SAS expander 202a and through a second SAS expander 202b to the
port (e.g., output port 510) of the device. For example, a second
OPEN request by an initiator on input port 504 may be routed by the
first expander 202a on an alternate path (e.g., 1014 or 1016) via
the IEL path 430 connecting the first expander 202a and a second
expander 202b.
[0067] In a fourth step 1208, the method 1200 for back-off retry in
a single, cohesive SAS expander 1100 includes determining link
availability between the second SAS expander and the port of the
device. For example, the second SAS expander 202b may indicate phy
blocking by sending a vendor unique status "SAS PRIMITIVE" back to
the first SAS expander 202a. Then, the first SAS expander 202a may
receive the SAS PRIMITIVE status from the second SAS expander
202b.
[0068] In a fifth step 1210, the method 1200 for back-off retry in
a single, cohesive SAS expander 1100 includes, upon determination
of a failed link or a busy link, re-routing the data transfer from
the second SAS expander 202b to the first SAS expander 202a or a
third SAS expander (e.g., 202c or 202d), or retrying the data
transfer through the second SAS expander 202b. For example, upon
receiving the blocked connection SAS PRIMITIVE status from the
second expander 202b, the first SAS expander 202b may re-route the
data transfer to another SAS expander (e.g., first SAS expander
202a or a third SAS expander, such as 202c or 202d). This process
may be repeated until a phy on one of the SAS expanders becomes
available, allowing the first connection to complete on any of the
expanders to be used to complete the connection to the output port
510.
[0069] Referring generally to FIG. 13, a method 1300 for back-off
retry in a single, cohesive SAS expander is illustrated in
accordance with the present disclosure. In a first step 1302, the
method 1300 for back-off retry in a single, cohesive SAS expander
1100 includes routing a data transfer between an input (e.g., input
ports 502 . . . 508) of a single, cohesive SAS expander and an
output (e.g., output ports 510 . . . 516) of the single, cohesive
SAS expander. The single, cohesive expander 1100 includes a first
SAS expander 202a, and at least one additional SAS expander (e.g.,
202b, 202c, or 202d), wherein the first SAS expander is connected
to the at least one additional SAS expander via at least one
inter-expander link (IEL) (e.g., 430 . . . 435).
[0070] In a second step 1304, the method 1300 for back-off retry
includes determining link availability between the first SAS
expander 202a and a port (e.g., output port 510 . . . 516) of a
device. For example, a link may become unavailable because it has
failed or is busy due to a physical or logical malfunction between
the SAS expander 202a and an intended destination output port 510 .
. . 516.
[0071] In a third step 1306, the method 1300 for back-off retry
includes, upon determination of a failed link or a busy link
between the first SAS expander and the port of the device,
re-routing the data transfer of the first SAS expander 202a to a
second SAS expander 202b. For example, the data transfer may be
re-routed from the first SAS expander 202a to a second SAS expander
202b via an IEL path connecting at least one phy for the first SAS
expander for inter-expander communications to at least one phys of
the second SAS expander for inter-expander communications.
[0072] In a fourth step 1308, the method 1300 for back-off retry
includes determining link availability between the second SAS
expander 202b and the port (e.g., output port 510) of the device.
As previously described above, the second SAS expander 202b may
indicate phy blocking by sending a vendor unique status "SAS
PRIMITIVE" back to the first SAS expander 202a. Then, the first SAS
expander 202a may receive the SAS PRIMITIVE status from the second
SAS expander 202b.
[0073] In a fifth step 1310, the method 1300 for back-off retry
includes, upon determination of a failed link or a busy link
between the second SAS expander and the port of the device,
re-routing the data transfer from the second SAS expander 202b to
the first SAS expander 202a or to a third SAS expander (e.g., 202c
or 202d), or retrying the data transfer through the second SAS
expander 202b. For example, upon receiving the blocked connection
SAS PRIMITIVE status from the second expander 202b, the first SAS
expander 202b may re-route the data transfer to another SAS
expander (e.g., first SAS expander 202a or a third SAS expander,
such as 202c or 202d). This process may be repeated until a phy on
one of the SAS expanders becomes available, allowing the first
connection to complete on either of the expanders to be used to
complete the connection to the destination port (e.g., output port
510).
[0074] In the present disclosure, the methods disclosed may be
implemented as sets of instructions or software readable by a
device. Such software may a computer program product which employs
a computer-readable storage medium including stored computer code
which is used to program a computer to perform the disclosed
function and process of the present invention. The
computer-readable medium may include, but is not limited to, any
type of conventional floppy disk, optical disk, CD-ROM, magnetic
disk, hard disk drive, magneto-optical disk, ROM, RAM, EPROM,
EEPROM, magnetic or optical card, or any other suitable media for
storing electronic instructions. Further, it is understood that the
specific order or hierarchy of steps in the methods disclosed are
examples of exemplary approaches. Based upon design preferences, it
is understood that the specific order or hierarchy of steps in the
method can be rearranged while remaining within the disclosed
subject matter. The accompanying method claims present elements of
the various steps in a sample order, and are not necessarily meant
to be limited to the specific order or hierarchy presented.
[0075] It is believed that the present disclosure and many of its
attendant advantages will be understood by the foregoing
description, and it will be apparent that various changes may be
made in the form, construction and arrangement of the components
without departing from the disclosed subject matter or without
sacrificing all of its material advantages. The form described is
merely explanatory, and it is the intention of the following claims
to encompass and include such changes.
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