U.S. patent application number 12/783578 was filed with the patent office on 2011-11-24 for energy-saving operation of a storage device.
This patent application is currently assigned to International Business Machines Corporation. Invention is credited to Doron Chen, George Goldberg, Roger Kahn, Ronen Itshak Kat, Kalman Zvi Meth, Julian Satran.
Application Number | 20110286130 12/783578 |
Document ID | / |
Family ID | 44972346 |
Filed Date | 2011-11-24 |
United States Patent
Application |
20110286130 |
Kind Code |
A1 |
Goldberg; George ; et
al. |
November 24, 2011 |
ENERGY-SAVING OPERATION OF A STORAGE DEVICE
Abstract
A computer implemented method is disclosed, for energy-saving
operation of a storage device with a read/write head. The method
includes monitoring workload of the storage device, calculating
current mean workload and adjusting seek speed of the read/write
head of the storage device to one of a plurality seek speeds
depending on the calculated current mean workload. The step of
adjusting the seek speed of the read/write head includes adjusting
the seek speed of the read/write head to be a first seek speed if
the calculated current mean workload is below a first threshold,
adjusting the seek speed of the read/write head to be a second seek
speed if the calculated current mean workload is between the first
threshold and a second threshold, and adjusting the seek speed of
the read/write head to be the first seek speed if the calculated
current mean workload is greater than the second threshold. A
computer program product and a data processing system are also
disclosed.
Inventors: |
Goldberg; George; (Bat-Yam,
IL) ; Chen; Doron; (Kfar-Saba, IL) ; Kahn;
Roger; (Jerusalem, IL) ; Kat; Ronen Itshak;
(Kfar-Saba, IL) ; Meth; Kalman Zvi; (Netanya,
IL) ; Satran; Julian; (Atlit, IL) |
Assignee: |
International Business Machines
Corporation
Armonk
NY
|
Family ID: |
44972346 |
Appl. No.: |
12/783578 |
Filed: |
May 20, 2010 |
Current U.S.
Class: |
360/75 ;
G9B/21.003 |
Current CPC
Class: |
G11B 5/5547
20130101 |
Class at
Publication: |
360/75 ;
G9B/21.003 |
International
Class: |
G11B 21/02 20060101
G11B021/02 |
Claims
1. A computer implemented method for energy savings for operation
of a storage device with a read/write head, the method comprising:
monitoring workload of the storage device; calculating current mean
workload; and adjusting seek speed of the read/write head of the
storage device to one of a plurality seek speeds depending on the
calculated current mean workload, wherein adjusting the seek speed
of the read/write head includes: adjusting the seek speed of the
read/write head to be a first seek speed if the calculated current
mean workload is below a first threshold; adjusting the seek speed
of the read/write head to be a second seek speed if the calculated
current mean workload is between the first threshold and a second
threshold; and adjusting the seek speed of the read/write head to
be the first seek speed if the calculated current mean workload is
greater than the second threshold.
2. A computer implemented method as claimed in claim 1, wherein
adjusting the seek speed of the read/write head of the storage
device includes: adjusting the seek speed of the read/write head to
be a first seek speed if the calculated current mean workload is
below a first threshold, and setting the seek speed of the
read/write head to be a second seek speed if the calculated current
mean workload is above the first threshold.
3. A computer implemented method as claimed in claim 1, wherein
monitoring the workload includes monitoring a characteristic of the
workload, which is selected from the group of workload
characteristics consisting of: disk utilization, idle time between
consecutive I/O requests, number of concurrent I/O requests,
condition of an I/O request cache and seek distance traveled by the
read/write head between consecutive I/O requests.
4. (canceled)
5. A computer implemented method as claimed in claim 1, wherein the
first seek speed is faster than the second seek speed.
6. A computer implemented method as claimed in claim 1, wherein the
storage device is a hard disk drive.
7. A computer implemented method as claimed in claim 6, wherein
adjusting the seek speed of the read/write head comprises adjusting
an acoustic mode of the hard disk drive.
8. A computer program product stored on a non-transitory tangible
computer readable storage medium for energy-saving operation of a
storage device with a read/write head, the computer program
including code for monitoring workload of the storage device;
calculating current mean workload; and adjusting seek speed of the
read/write head of the storage device to one of a plurality seek
speeds depending on the calculated current mean workload, wherein
the computer program code for adjusting the seek speed further
including: adjusting the seek speed of the read/write head to be a
first seek speed if the calculated current mean workload is below a
first threshold; adjusting the seek speed of the read/write head to
be a second seek speed if the calculated current mean workload is
between the first threshold and a second threshold; and adjusting
the seek speed of the read/write head to be the first seek speed if
the calculated current mean workload is greater than the second
threshold.
9. A computer program product as claimed in claim 8, wherein the
computer program includes code for adjusting the seek speed of the
read/write head to be a first seek speed if the calculated current
mean workload is below a first threshold, and for adjusting the
seek speed of the read/write head to be a second seek speed if the
calculated current mean workload is above the first threshold.
10. A computer program product as claimed in claim 8, wherein
monitoring the workload includes monitoring a characteristic of the
workload, which is selected from the group of workload
characteristics consisting of: disk utilization, idle time between
consecutive I/O requests, number of concurrent I/O requests,
condition of an I/O request cache and seek distance traveled by the
read/write head between consecutive I/O requests.
11. (canceled)
12. A computer program product as claimed in claim 8, wherein the
first seek speed is faster than the second seek speed.
13. A computer program product as claimed in claim 8, wherein the
storage device is a hard disk drive.
14. A computer program product as claimed in claim 13, wherein
adjusting the first seek speed comprises adjusting an acoustic mode
of the hard disk drive.
15. An energy savings data processing system comprising: a
processor; a storage device with a read/write head; a computer
usable medium connected to the processor for storing a computer
program that includes a set of instructions to be executed by the
processor, the set of instructions including: monitoring workload
of the storage device; calculating current mean workload; and
adjusting seek speed of the read/write head of the storage device
to one of a plurality seek speeds depending on the calculated
current mean workload, wherein adjusting the seek speed of the
read/write head includes: adjusting the seek speed of the
read/write head to be a first seek speed if the calculated current
mean workload is below a first threshold; adjusting the seek speed
of the read/write head to be a second seek speed if the calculated
current mean workload is between the first threshold and a second
threshold; and adjusting the seek speed of the read/write head to
be the first seek speed if the calculated current mean workload is
greater than the second threshold.
16. A data processing system as claimed in claim 15, wherein
adjusting the seek speed of the read/write head includes: adjusting
the seek speed of the read/write head to be a first seek speed if
the calculated current mean workload is below a first threshold,
and adjusting the seek speed of the read/write head to be a second
seek speed if the calculated current mean workload is above the
first threshold.
17. A data processing system as claimed in claim 15, wherein
monitoring the workload includes monitoring a characteristic of the
workload, which is selected from the group of workload
characteristics consisting of: disk utilization, idle time between
consecutive I/O requests, number of concurrent I/O requests,
condition of an I/O request cache and seek distance traveled by the
read/write head between consecutive I/O requests.
18. (canceled)
19. A data processing system as claimed in claim 15, wherein the
first seek speed is faster than the second seek speed.
20. A data processing system as claimed in claim 15, wherein the
storage device is a hard disk drive.
21. A data processing system as claimed in claim 20, wherein
adjusting the seek speed comprises adjusting an acoustic mode of
the hard disk drive.
Description
BACKGROUND
[0001] The present invention relates to energy saving. More
specifically, the present invention relates to an energy-saving
operation of a storage device which has a movable read/write
head.
[0002] There is little doubt today as to the need for energy
saving. Electrical energy conservation is an important element of
energy policy, reducing energy consumption and demand, in the
attempt to balance the increasing energy demand of the world's
growing population with the decline of energy resources and soaring
energy costs. Reducing power consumption in computer systems has
undoubtedly become an important issue.
[0003] A hard disk drive device typically includes one or more flat
disks called platters (42, see FIG. 4), which are coated with a
layer of magnetic material, onto which data is recorded or read by
a head (hereinafter--read/write head, 46, see FIG. 4) held by an
actuator arm (48, FIG. 4) and actuated by an actuator (43, FIG. 4)
to move across the platter (indicated by arrows in FIG. 4). The
platter is coupled to and rotated by a spindle (44, FIG. 4). By
incorporating rotation of the platter with motion of the head over
the platter it is possible to bring the head over a desired data
block and write onto it or read it.
[0004] Hard disks are typically provided with an acoustic
management capability, which facilitates control over the level of
noise generated by the hard disk drive. In hard disk drives with
acoustic management the seek speed of the read/write head (i.e. the
speed at which it is moved to reach its target position) is
controlled. In many such hard disk drives several seek speeds are
available (also refereed to as "acoustic modes").
[0005] Attempts were made to reduce the acoustic noise of disk
storage. For example, it was proposed in the past to actively
control the seek speed so that the head arrives at its destination
only just in time to read the desired data block, rather than
arriving as quickly as possible and then having to wait for the
data block to come around (phenomenon known as the "rotational
latency").
[0006] Another way of reducing energy consumption was to reduce the
spin speed of storage disks to reduce energy consumption and
generate less waste heat.
SUMMARY
[0007] According to embodiments of the present invention there is
provided a computer implemented method for energy-saving operation
of a storage device with a read/write head. The method includes
monitoring workload of the storage device, calculating a current
mean workload of the storage device and adjusting seek speed of the
read/write head to one of a plurality of seek speeds depending on
the calculated current mean workload.
[0008] Furthermore, in accordance with embodiments of the present
invention, there is provided a computer program product stored on a
non-transitory tangible computer readable storage medium for
energy-saving operation of a storage device with a read/write head.
The computer program includes code for monitoring workload of the
storage device, calculating a current mean workload and for
adjusting seek speed of the read/write head to one of a plurality
seek speeds depending on the calculated current mean workload.
[0009] Furthermore, in accordance with embodiments of the present
invention, there is provided an energy saving data processing
system. The system includes a processor; a storage device with a
read/write head; a computer usable medium connected to the
processor for storing a computer program that includes a set of
instructions to be executed by the processor. The set of
instructions includes monitoring workload of the storage device,
calculating a current mean workload and adjusting seek speed of the
read/write head to one of a plurality seek speeds depending on the
calculated current mean workload.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The subject matter regarded as the invention is particularly
pointed out and distinctly claimed in the concluding portion of the
specification. The invention, however, both as to organization and
method of operation, together with objects, features, and
advantages thereof, may best be understood by reference to the
following detailed description when read with the accompanying
drawings in which:
[0011] FIG. 1A is a table presenting a comparison between energy
consumption of a given hard disk drive (1TB 3.5'' Hitachi) at
different (read) workloads.
[0012] FIG. 1B is a table presenting comparison of energy
consumption of a SPC-1 like (Storage Performance Council standard)
workload at various I/O (Input-Output) rates.
[0013] FIG. 2 is a flow chart of a method for energy-saving
operation of a storage device with a read/write head, according to
embodiments of the present invention.
[0014] FIG. 3 is a flow chart of a method for energy-saving
operation of a storage device with a read/write head, which
includes monitoring current mean number of read/write requests in
the queue, according to embodiments of the present invention.
[0015] FIG. 4 illustrates a hard disk drive incorporated in a
computer system, according to embodiments of the present
invention.
DETAILED DESCRIPTION
[0016] As will be appreciated by one skilled in the art, aspects of
the present invention may be embodied as a system, method or
computer program product. Accordingly, aspects of the present
invention may take the form of an entirely hardware embodiment, an
entirely software embodiment (including firmware, resident
software, micro-code, etc.) or an embodiment combining software and
hardware aspects that may all generally be referred to herein as a
"circuit," "module" or "system." Furthermore, aspects of the
present invention may take the form of a computer program product
embodied in one or more computer readable medium(s) having computer
readable program code embodied thereon.
[0017] Any combination of one or more computer readable medium(s)
may be utilized. The computer readable medium may be a computer
readable signal medium or a computer readable storage medium. A
computer readable storage medium may be, for example, but not
limited to, an electronic, magnetic, optical, electromagnetic,
infrared, or semiconductor system, apparatus, or device, or any
suitable combination of the foregoing. More specific examples (a
non-exhaustive list) of the computer readable storage medium would
include the following: an electrical connection having one or more
wires, a portable computer diskette, a hard disk, a random access
memory (RAM), a read-only memory (ROM), an erasable programmable
read-only memory (EPROM or Flash memory), an optical fiber, a
portable compact disc read-only memory (CD-ROM), an optical storage
device, a magnetic storage device, or any suitable combination of
the foregoing. In the context of this document, a computer readable
storage medium may be any non-transitory, tangible medium that can
contain, or store a program for use by or in connection with an
instruction execution system, apparatus, or device.
[0018] A computer readable signal medium may include a propagated
data signal with computer readable program code embodied therein,
for example, in baseband or as part of a carrier wave. Such a
propagated signal may take any of a variety of forms, including,
but not limited to, electro-magnetic, optical, or any suitable
combination thereof. A computer readable signal medium may be any
computer readable medium that is not a computer readable storage
medium and that can communicate, propagate, or transport a program
for use by or in connection with an instruction execution system,
apparatus, or device.
[0019] Program code embodied on a computer readable medium may be
transmitted using any appropriate medium, including but not limited
to wireless, wireline, optical fiber cable, RF, etc., or any
suitable combination of the foregoing.
[0020] Computer program code for carrying out operations for
aspects of the present invention may be written in any combination
of one or more programming languages, including an object oriented
programming language such as Java, Smalltalk, C++ or the like and
conventional procedural programming languages, such as the "C"
programming language or similar programming languages. The program
code may execute entirely on the user's computer, partly on the
user's computer, as a stand-alone software package, partly on the
user's computer and partly on a remote computer or entirely on the
remote computer or server. In the latter scenario, the remote
computer may be connected to the user's computer through any type
of network, including a local area network (LAN) or a wide area
network (WAN), or the connection may be made to an external
computer (for example, through the Internet using an Internet
Service Provider).
[0021] Aspects of the present invention are described below with
reference to flowchart illustrations and/or block diagrams of
methods, apparatus (systems) and computer program products
according to embodiments of the invention. It will be understood
that each block of the flowchart illustrations and/or block
diagrams, and combinations of blocks in the flowchart illustrations
and/or block diagrams, can be implemented by computer program
instructions. These computer program instructions may be provided
to a processor of a general purpose computer, special purpose
computer, or other programmable data processing apparatus to
produce a machine, such that the instructions, which execute via
the processor of the computer or other programmable data processing
apparatus, create means for implementing the functions/acts
specified in the flowchart and/or block diagram block or
blocks.
[0022] These computer program instructions may also be stored in a
computer readable medium that can direct a computer, other
programmable data processing apparatus, or other devices to
function in a particular manner, such that the instructions stored
in the computer readable medium produce an article of manufacture
including instructions which implement the function/act specified
in the flowchart and/or block diagram block or blocks.
[0023] The computer program instructions may also be loaded onto a
computer, other programmable data processing apparatus, or other
devices to cause a series of operational steps to be performed on
the computer, other programmable apparatus or other devices to
produce a computer implemented process such that the instructions
which execute on the computer or other programmable apparatus
provide processes for implementing the functions/acts specified in
the flowchart and/or block diagram block or blocks.
[0024] Flowchart's and block diagram/s in the figures illustrate
the architecture, functionality, and operation of possible
implementations of systems, methods and computer program products
according to various embodiments of the present invention. In this
regard, each block in the flowchart or block diagrams may represent
a module, segment, or portion of code, which comprises one or more
executable instructions for implementing the specified logical
function(s). It should also be noted that, in some alternative
implementations, the functions noted in the block may occur out of
the order noted in the figures. For example, two blocks shown in
succession may, in fact, be executed substantially concurrently, or
the blocks may sometimes be executed in the reverse order,
depending upon the functionality involved. It will also be noted
that each block of the block diagrams and/or flowchart
illustration, and combinations of blocks in the block diagrams
and/or flowchart illustration, can be implemented by special
purpose hardware-based systems that perform the specified functions
or acts, or combinations of special purpose hardware and computer
instructions.
[0025] According to embodiments of the present invention it is
proposed to control the operation of a read/write head of a storage
device, such as, for example, a hard disk drive, in an
energy-saving manner, i.e. to minimize the energy consumption for a
given disk-access scenario. To achieve this it is proposed to
employ different seek speeds of the read/write head in a manner
which is hereinafter described.
[0026] The present invention is applicable for single-disk storage
devices as well as for multiple-disk storage devices.
[0027] According to embodiments of the present invention the
overall disk seek energy consumption is controlled based on the
monitoring disk workload and utilization, and calculating a current
mean workload. Acoustic mode change is effective for energy
savings, for example, if one of the following situations holds:
[0028] 1. An appropriate workload is identified with reference to
workload characteristics, such as, for example, operation type
(read/write), transfer size and access type (random/sequential).
The disk acoustic mode may be changed during a predefined current
mean workload, which may be determined by monitoring one or more
workload characteristics and calculating the current mean workload,
per a given time interval. Predetermined specific threshold values
may vary, depending on the type of the storage device.
[0029] 2. An appropriate disk utilization scenario is identified
based on idle time and the length of the disk queue. If there is
enough idle time then the disk seek time may be increased (at the
expense of disk idle time). If the concurrency level of I/O
operations is high enough, then a lower seek speed may be
chosen.
[0030] Energy saving, according to embodiments of the present
invention, may be achieved by applying the appropriate seek speed
according to the calculated current mean workload.
[0031] Changing the acoustic modes of a disk drive changes power
consumption of the disk drive. Since the feature was originally
implemented to reduce noise and friction, the higher power mode is
usually called "normal mode" (or "performance mode") and the lower
power mode is usually called "quiet mode". A hard disk drive may
have more than two acoustic modes. For example, in the SATA
specification, 128 seek modes are defined.
[0032] This feature allows the disk user system, whether having a
single disk storage system, Redundant Array of Independent Disks
(RAID) or any other configuration, to adjust the seek speed of the
disk head. Reducing the seek speed of the disk head also decreases
the power dissipation of the disk drive. According to embodiments
of the present invention, this feature can be exploited to reduce
disk energy consumption.
[0033] It is evident, when considering the power consumption of a
hard disk drive, that for some workloads the energy consumption
(defined as power consumption over time) actually increases when
using quiet acoustic mode for the same workload. However, in some
cases, energy reduction is present. Therefore, using quiet mode for
every workload in order to save energy is not advised.
[0034] FIG. 1A is a table presenting a comparison between energy
consumption of a given hard disk drive at different (read)
workloads. The information in this table is based on tests carried
out by the inventors of the present invention on a specific hard
disk drive--1TB 3.5'' Hitachi.
[0035] It is evident from that table that for a small number (1, 2)
of concurrent read requests changing the acoustic mode of the disk
drive from normal mode to quiet mode would result in an increase in
energy consumption. However at a certain threshold number of
concurrent requests changing the acoustic mode of the disk drive
from normal mode to quiet mode would result in a decrease in energy
consumption (4 requests).
[0036] However, over a second, higher threshold number of
concurrent read requests, changing the acoustic mode of the disk
drive from normal mode to quiet mode may again result in an
increase of energy consumption and degraded performance.
[0037] FIG. 1B is a table presenting comparison of energy
consumption of a SPC-1 like (Storage Performance Council standard)
workload at various I/O (Input-Output) rates.
[0038] One may conclude that for a given type of storage device
there is a first current mean workload threshold below which it
would be recommended to operate a storage device at normal mode
(i.e. operating the read/write head at a first seek speed) and over
which it would be recommended to operate the storage device at
quiet mode (i.e. operating the read/write head at a second seek
speed, which is slower than the first seek speed) to achieve energy
saving. Furthermore, there is a second current mean workload
threshold over which it would be recommended to operate the storage
device at normal mode again, to save energy and maintain a
sustainable performance level.
[0039] When operating the storage device in accordance with
embodiments of the present invention no data needs to be moved, no
caching is required, nor is any other data manipulation needed. An
algorithm may be used to operate a storage device according to
embodiments of the present invention.
[0040] Operating a storage device according to embodiments of the
present invention would reduce the overall energy consumed by the
device. Operating a storage device according to embodiments of the
present invention may be used in conjunction with other
energy-saving methods in order to reduce power dissipation further
than would be achieved by any one of these methods alone.
[0041] According to embodiments of the present invention it is
suggested to characterize workload of the storage device, and
monitor the workload and disk utilization (the term workload, for
the context of the present invention is understood to include both
disk workload and disk utilization), in order to optimize energy
consumption of the hard disk drive. Current mean workload is
calculated form the monitored workload information, and
consequently the seek speed of the read/write head is adjusted
based on the calculated current mean workload (e.g. by setting
different acoustic modes of the disk) in a predetermined manner, as
is described hereinafter.
[0042] Workload may be determined by considering one or more of the
following parameters: operation type (read/write), transfer size,
access type (random/sequential), and disk utilization. Disk
utilization may be determined by considering one or more of the
following parameters: idle time, disk queue, and response time.
[0043] The "current mean workload" is calculated by considering a
predetermined time interval, and calculating the mean value of the
specific workload characteristic that is monitored over a current
time interval. The length of the time interval may be selected
arbitrarily.
[0044] Workload characteristics for consideration, according to
embodiments of the present invention, may include, for example,
disk utilization, idle time between consecutive read/write (or I/O)
requests, number of concurrent I/O requests, condition of the I/O
request cache (how full it is) and seek distance traveled by the
read/write head between consecutive read/write requests.
[0045] FIG. 2 is a flow chart of a method for energy-saving
operation of a storage device with a read/write head, according to
embodiments of the present invention.
[0046] The method includes monitoring workload of the storage
device (20) and calculating a current mean workload (CMW) of the
storage device (21). It is then determined whether the CMW is below
a predetermined threshold (22) and the seek speed of the read/write
head of the storage device is adjusted to one of a plurality seek
speeds depending on the monitored current workload (24, 26). The
calculated CMW is compared to a threshold (22). If the CMW is below
that threshold then the seek speed of the read/write head is set to
be a first seek speed (24). If the CMW is not below that threshold
(that is--equal or greater than the threshold) then the seek speed
of the read/write head is set to be a second seek speed (26).
[0047] A method for energy-saving operation of a storage device
with a read/write head, according to embodiments of the present
invention, may be performed in a feedback loop manner.
[0048] A control algorithm for energy-saving operation of a storage
device, according to embodiments of the present invention, may
include the following steps:
[0049] For a given time interval:
[0050] a) If one or more of the following current conditions is met
adjust seek speed of the read/write head of the hard disk drive to
a first low value:
[0051] i. Current mean disk utilization is below a predetermined
threshold T'.sub.1;
[0052] ii. Current mean idle time between consecutive I/O requests
is greater than threshold T'.sub.2;
[0053] iii. Current mean number of concurrent I/O requests is
greater than threshold T'.sub.3;
[0054] b) If one or more of the following current conditions is met
adjust seek speed of the read/write head of the storage device to a
second value (higher than the first value):
[0055] i. Current mean disk utilization is greater than threshold
T'.sub.1;
[0056] ii. Current mean idle time between consecutive I/O requests
is smaller than threshold T'.sub.2;
[0057] iii. Current mean number of concurrent requests in the queue
(disk, controller, or operating system queue) is less than
T'.sub.3;
[0058] iv. Currently I/O request queue is full.
[0059] T.sub.1 and T.sub.1', (as well as T.sub.2 and T.sub.2',
T.sub.3 and T.sub.3', respectively) are related as referring to the
same "threshold", yet they are defined as having different (perhaps
just slightly different) values so as to avoid erratic fluctuations
in seek speed of the read/write head of the storage device.
[0060] According to other embodiments of the present invention the
read/write head of the storage device may be adjusted to operate in
a low seek speed value (quiet mode) when the current workload
matches one or more of the following current conditions:
[0061] i. Current mean idle time between consecutive requests is
between a first threshold idle time T.sub.idle1 and a second
threshold idle time T.sub.idle2;
[0062] ii. Current number of I/O requests in the queue (disk,
controller, or operating system queue) is between threshold
Q.sub.min and threshold Q.sub.max,
[0063] iii. Current mean seek distance traveled by the read/write
head between consecutive read/write requests is smaller than a seek
distance Seek.sub.min, where Seek.sub.min depends on the type of
disk. Example Seek.sub.min can be 100 cylinders.
[0064] Note that actual values of the workload characteristics
thresholds may vary, depending on the specific hard disk drive type
(and its working parameters, such as, for example, typical seek
speeds, rotational velocity of the disk platters). Determining the
threshold may require some testing or knowledge of specific disk
characteristics as provided by the hard disk drive
manufacturer.
[0065] In order to appreciate orders and scales of the
abovementioned thresholds values consider for example,
T.sub.idle1=5 ms, T.sub.idle2=500 ms, Q.sub.depth-min=4,
Q.sub.depth-max=16. These values are not necessarily the threshold
values that would be used for any given type of hard disk drive, as
actual threshold values depend on the specific type of hard disk
drive.
[0066] FIG. 3 is a flow chart of a method for energy-saving
operation of a storage device with a read/write head, which
includes monitoring current number of read/write requests in the
queue, according to embodiments of the present invention.
[0067] The method includes monitoring current number of concurrent
I/O requests in the queue (disk, controller, or operating system
queue) (30) and calculating a current mean number of concurrent I/O
requests (CMCR) (31). The CMCR is compared with a first threshold
(32). If CMCR is below the first threshold then the seek speed of
the read/write head is set to be a first seek speed (34). If CMCR
is not below the first threshold it is compared with a
second--higher--threshold (33). If CMCR is below the second
threshold then the seek speed of the read/write head is set to be a
second seek speed (36). If CMCR is not below the first and the
second thresholds (i.e. equal or greater than the second threshold)
then the seek speed of the read/write head is set to be the first
seek speed (34). In this example, the first seek speed is higher
than the second seek speed. It should be clear to those skilled in
the art that it is possible to utilize multiple (more than 2) seek
speeds to achieve energy savings, if more such seek speeds
(acoustic modes) are available.
[0068] For practical purposes, in order to prevent fluctuations on
the operation of the disk, it may be advantageous to choose a
specific value for the current workload threshold which when
exceeded will cause the seek speed of the read/write head to be
changed from a first speed to a second speed, but assign a slightly
different value to the same threshold so that when the current
workload drops below that threshold the seek speed of the
read/write head will be changed back to its first speed.
[0069] FIG. 4 illustrates a hard disk drive (40) incorporated in a
data processing system, according to embodiments of the present
invention.
[0070] The data processing system includes a hard disk drive (40)
which includes one or more platters (42) onto which data may be
recorded or read by a read/write head (46) held by an actuator arm
(48) actuated by an actuator (43) which moves the head across the
platter to be placed over a desired data block. The platter is
coupled to and rotated by a spindle (44). A controller (41)
controls the operation of the hard disk drive, and is connected to
a processor (45). Also may be included an I/O interface device (49)
and display or other peripheral device (47).
[0071] The controller (41) may set the seek speed of the read/write
head (46) of the hard disk drive (40) as dictated by an algorithm
for energy-saving operation of a hard disk drive, according to
embodiments of the present invention.
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