U.S. patent application number 16/667249 was filed with the patent office on 2021-04-29 for tape-creep detection via frequency domain data.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Richard Bradshaw, Nhan Xuan Bui, Lee Curtis Randall, Daniel James Winarski.
Application Number | 20210125632 16/667249 |
Document ID | / |
Family ID | 1000004479792 |
Filed Date | 2021-04-29 |
United States Patent
Application |
20210125632 |
Kind Code |
A1 |
Winarski; Daniel James ; et
al. |
April 29, 2021 |
TAPE-CREEP DETECTION VIA FREQUENCY DOMAIN DATA
Abstract
A tape drive may arrange timing-based-servo marks into a
timing-based-servo pattern. The timing-based-servo pattern may be
at least one M-pattern. The tape drive may select the at least one
M-pattern. The tape drive may match at least two timing-based-servo
marks in the at least one M-pattern. The tape drive may determine,
from the matching, whether an alignment of the at least two
timing-based-servo marks is demonstrative of tape-creep.
Inventors: |
Winarski; Daniel James;
(Tucson, AZ) ; Bui; Nhan Xuan; (Tucson, AZ)
; Randall; Lee Curtis; (Tucson, AZ) ; Bradshaw;
Richard; (Tucson, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
1000004479792 |
Appl. No.: |
16/667249 |
Filed: |
October 29, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11B 20/1202 20130101;
G11B 5/534 20130101; G11B 5/5928 20130101; G11B 5/5508 20130101;
G11B 5/78 20130101; G11B 2020/1281 20130101 |
International
Class: |
G11B 5/592 20060101
G11B005/592; G11B 5/55 20060101 G11B005/55; G11B 5/53 20060101
G11B005/53; G11B 5/78 20060101 G11B005/78; G11B 20/12 20060101
G11B020/12 |
Claims
1. A method for allowing a tape drive to read from a tape cartridge
with timing-based-servo marks, wherein the tape cartridge is a
dual-reel tape cassette that stores a tape-media, the method
comprising: arranging the timing-based-servo marks into a
timing-based-servo pattern, wherein the timing-based-servo pattern
is at least one M-pattern; selecting the at least one M-pattern;
matching at least two timing-based-servo marks in the at least one
M-pattern; and determining, from the matching, whether an alignment
of the at least two timing-based-servo marks is demonstrative of
tape-creep, wherein the tape-creep is determined for the tape-media
stored in the dual-reel tape cassette.
2. The method of claim 1, wherein the timing-based-servo pattern
includes: a first set of servo marks that include five consecutive
angled lines directed toward a midway of the timing-based-servo
pattern and which touch a second set of servo marks, the second set
of servo marks include five consecutive angled lines directed away
from the midway of the timing-based-servo pattern and which touch a
third set of servo marks, the third set of servo marks include five
consecutive angled lines directed away from the midway of the
timing-based-servo pattern and which touch a fourth set of servo
marks, and the fourth set of servo marks include five consecutive
angled lines directed toward the midway of the timing-based-servo
pattern.
3. The method of claim 1, wherein the timing-based-servo pattern is
from a European Computer Manufacturers Association (ECMA)-319 tape
cartridge.
4. The method of claim 1, further comprising: detecting the
timing-based-servo marks on the tape cartridge; and assembling,
electronically, the timing-based-servo marks into the at least one
M-pattern.
5. The method of claim 1, wherein the timing-based-servo marks are
written at a 45-degree angle relative to a servo track of a
magnetic media.
6. (canceled)
7. (canceled)
8. The method of claim 1, further comprising: recording data in the
tape cartridge in a parallel-serpentine pattern.
9. The method of claim 1, wherein determining whether the alignment
is demonstrative of tape-creep comprises: comparing, during a read
operation, the slope against a threshold; identifying that the
threshold has been exceeded; reading all data from the tape
cartridge; and transferring all data to a second tape
cartridge.
10. The method of claim 9, further comprising: alerting a user,
with an indication, that the match threshold has been exceeded.
11. A system comprising: a tape drive; and a tape cartridge with
timing-based-servo marks, wherein the tape cartridge is a dual-reel
tape cassette that stores a tape-media, wherein the tape drive
reads from the tape cartridge, and wherein the tape drive is
configured to perform the operations comprising: arranging the
timing-based-servo marks into a timing-based-servo pattern, wherein
the timing-based-servo pattern is at least one M-pattern; selecting
the at least one M-pattern; matching at least two
timing-based-servo marks in the at least one M-pattern; and
determining, from the matching, whether an alignment of the at
least two timing-based-servo marks is demonstrative of tape-creep,
and wherein the tape-creep is determined for the tape-media stored
in the dual-reel tape cassette.
12. The system of claim 11, wherein the timing-based-servo pattern
includes: a first set of servo marks that include five consecutive
angled lines directed toward a midway of the timing-based-servo
pattern and which touch a second set of servo marks, the second set
of servo marks include five consecutive angled lines directed away
from the midway of the timing-based-servo pattern and which touch a
third set of servo marks, the third set of servo marks include five
consecutive angled lines directed away from the midway of the
timing-based-servo pattern and which touch a fourth set of servo
marks, and the fourth set of servo marks include five consecutive
angled lines directed toward the midway of the timing-based-servo
pattern.
13. The system of claim 11, wherein the timing-based-servo pattern
is from a European Computer Manufacturers Association (ECMA)-319
tape cartridge.
14. The system of claim 11, wherein the operations further
comprise: detecting the timing-based-servo marks on the tape
cartridge; and assembling, electronically, the timing-based-servo
marks into the at least one M-pattern.
15. The system of claim 11, wherein the timing-based-servo marks
are written at a 45-degree angle relative to a servo track of a
magnetic media.
16. (canceled)
17. (canceled)
18. The system of claim 11, wherein the operations further
comprise: recording data in the tape cartridge in a helical-scan
pattern.
19. The system of claim 11, wherein determining whether the
alignment is demonstrative of tape-creep comprises: comparing,
during a read operation, the slope against a threshold; identifying
that the threshold has been exceeded; reading all data from the
tape cartridge; and transferring all data to a second tape
cartridge.
20. The system of claim 19, wherein the operations further
comprise: alerting a user, with an indication, that the match
threshold has been exceeded.
Description
BACKGROUND
[0001] The present disclosure relates generally to the field of
tape drive systems, and more specifically to automatically
detecting tape-creep via the tape drive itself.
[0002] The tape drive industry is constantly increasing the density
of magnetic tape and in doing so the tolerance budget of the
magnetic tape is shrinking. The shrinking tolerance budget results
in the magnetic tape being increasingly exposed to creep of the
polyethylene terephthalate substrate of the magnetic tape and creep
of the recording frontcoat of binders and nanoparticles of the
magnetic tape.
SUMMARY
[0003] Embodiments of the present disclosure include a method and
system for allowing a tape drive to read from a tape cartridge with
timing-based-servo marks. A tape drive may arrange
timing-based-servo marks into a timing-based-servo pattern. The
timing-based-servo pattern may be at least one M-pattern. The tape
drive may select the at least one M-pattern. The tape drive may
match at least two timing-based-servo marks in the at least one
M-pattern. The tape drive may determine, from the matching, whether
an alignment of the at least two timing-based-servo marks is
demonstrative of tape-creep.
[0004] The above summary is not intended to describe each
illustrated embodiment or every implementation of the present
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The drawings included in the present disclosure are
incorporated into, and form part of, the specification. They
illustrate embodiments of the present disclosure and, along with
the description, serve to explain the principles of the disclosure.
The drawings are only illustrative of certain embodiments and do
not limit the disclosure.
[0006] FIG. 1 illustrates an example of a timing-based-servo
system, in accordance with embodiments of the present
disclosure.
[0007] FIG. 2 depicts a block diagram of a timing-based-servo
control system, in accordance with embodiments of the present
disclosure.
[0008] FIG. 3A illustrates a frame of a timing-based-servo pattern,
in accordance with embodiments of the present disclosure.
[0009] FIG. 3B illustrates a frame of a timing-based-servo pattern
demonstrating tape-creep, in accordance with embodiments of the
present disclosure.
[0010] FIG. 4 illustrates a flowchart of an example method for
averaging the slope of timing-based-servo marks to determine
tape-creep, in accordance with embodiments of the present
disclosure.
[0011] FIG. 5 illustrates a flowchart of an example method for
identifying the gradient of slopes for three successive
timing-based-servo marks to determine tape-creep, in accordance
with embodiments of the present disclosure.
[0012] FIG. 6 illustrates a flowchart of an example method for
arranging timing-based-servo marks to determine tape-creep, in
accordance with embodiments of the present disclosure.
[0013] While the embodiments described herein are amenable to
various modifications and alternative forms, specifics thereof have
been shown by way of example in the drawings and will be described
in detail. It should be understood, however, that the particular
embodiments described are not to be taken in a limiting sense. On
the contrary, the intention is to cover all modifications,
equivalents, and alternatives falling within the spirit and scope
of the disclosure.
DETAILED DESCRIPTION
[0014] Aspects of the present disclosure relate generally to the
field of tape drive systems, and more specifically to automatically
detecting tape-creep via the tape drive itself. It should be noted
that a "tape drive" is a system that utilizes tape to store
information, further noted is that a "tape" is defined as a
flexible magnetic tape medium. While the present disclosure is not
necessarily limited to such applications, various aspects of the
disclosure may be appreciated through a discussion of various
examples using this context.
[0015] The tape drive industry is constantly increasing the density
of magnetic tape and in doing so the tolerance budget of the
magnetic tape is shrinking. The shrinking tolerance budget results
in the magnetic tape being increasingly exposed to creep of the
polyethylene terephthalate substrate of the magnetic tape (as it is
typically stored at high tension for long periods of time) and
creep of the recording frontcoat of binders and nanoparticles of
the magnetic tape. Accordingly, a tape-creep sensor would be highly
desirable at the tape drive level for high-density tape media used
by tape drives for data input/output (I/O).
[0016] The basic M-pattern timing-based-servo looks like this: /\/\
(e.g., four servo marks configured to look like an "M"). The
preferred implementation is that the M-pattern timing-based-servo
is constructed by a dedicated servo-writing head that writes the
M-pattern all at the same time. As discussed in regard to the
present disclosure however, an embodiment is contemplated where a
plurality of M-pattern timing-based-servo M's are written in a
5-5-5-5 M-pattern: /////\\\\\/////\\\\\.
[0017] In yet another embodiment, an M-Pattern is derived from
today's timing-based-servos, which looks like this pattern:
/////\\\\\////\\\\, e.g., a 5-5-4-4 M-pattern. By combining servo
marks as follows, in the first four servo marks in the first burst
/////, the last four servo marks in the second burst \\\\\, the
third burst ////, and the fourth burst \\\\, one to four suitable
M-patterns may be constructed (e.g., because the last/fifth servo
marks in the first and second bursts cannot be paired with any
other servo marks on the third and fourth bursts as they include
only four servo marks).
[0018] Regardless of if the 5-5-5-5 M-pattern or the 5-5-4-4
M-pattern is used for the purposes of this disclosure, a tape drive
system itself is able to detect potential tape-creep before
permanent errors result. Various thresholds are contemplated that
are used for detecting the potential tape-creep. In one instance, a
tighter, more restrictive threshold for write operations is
contemplated to prevent existing data on the magnetic tape from
being over-written, and a somewhat looser, less restrictive
threshold for read operations is contemplated so that data may be
read off the tape before the tape becomes unreadable. Further
thresholds and various embodiments are now discussed further in
regard to the FIGS.
[0019] Referring now to FIG. 1, illustrated an example of a
timing-based-servo system 100, in accordance with embodiments of
the present disclosure. In some embodiments, the timing-based-servo
system 100 includes tape head actuator 102, base plate 110,
actuator shaft 108, and tape 112.
[0020] In some embodiments, the tape head actuator 102 includes
narrow servo read heads 104 and data read/write head 106. Further,
the base plate 110 supports the actuator shaft 108 and the tape
head actuator 102 moves along the actuator shaft 108 in the lateral
Y direction via a servo motor or electromagnet (not shown).
Typically, the tape head actuator 102 includes or is connected to a
stepper motor arrangement for gross movements, and a voice coil
arrangement for fine movements. For simplicity, these details are
not shown.
[0021] In some embodiments, the tape 112 represents a portion of a
linear tape medium (e.g., electromagnetic tape, etc.) that is
ideally moving in the longitudinal X direction. The tape 112
includes a data track 114, shown with eight sub-tracks, sandwiched
between two servo marks 116A and 116B that have been imprinted
during the tape manufacturing process and/or logically arranged
during operation of the timing-based-servo system 100 with a
magnetic servo pattern 118 that consists of one or more servo marks
arranged in a 5-5-5-5 M-pattern (or, in some embodiments, a 5-5-4-4
M-pattern, which is not shown) and which transitions with two
different azimuthal angles, which will be described in greater
detail below. Although only a single data track 114 is shown, the
tape 112 typically has several data tracks separated by servo
marks. In addition, each data track typically includes several
sub-tracks, and the data read/write head 106 will include several
read/write heads.
[0022] In some embodiments, during operation(s), the tape 112 moves
in the longitudinal X direction past the tape head actuator 102.
The servo read heads 104, which are small in the lateral dimension
in comparison to the servo marks 116A and 116B, detect the servo
patterns 118 in the servo marks 116A and 116B. Based on the timing
of pulses generated by the servo read heads 104 reading the servo
patterns 118, the position in the lateral Y direction of the servo
read heads 104 relative to the position of the servo marks in the
lateral Z direction can be determined.
[0023] Typically, there is approximate movement of the tape 112 in
the lateral Z direction relative to the ideal longitudinal X
direction of travel. To keep the data read/write head 106 in good
alignment with the data track 114, a state variable feedback system
controls the servo that moves the tape head actuator 102 along the
actuator shaft 108 in the lateral Y direction based on the relative
position of the servo read heads 104 and the ideal position
relative to the servo marks 116A and 116B, which may be the
centerline of the servo marks 116A and 116B or may be a lateral
offset to that centerline.
[0024] Referring now to FIG. 2, depicted is a block diagram of a
timing-based-servo control system 200, in accordance with
embodiments of the present disclosure. In some embodiments, the
timing-based-servo control system 200 may be the timing-based-servo
system 100 and/or be an addition to the timing-based-servo system
100 of FIG. 1. In some embodiments, the servo control system 200 is
based on a position error signal loop utilizing a
proportional-integral-derivative (PID) controller 202. The servo
control system 200 includes the PID controller 202, an actuator
204, a head module 206, at least one servo read head 208 located in
or on the head module 206, a servo channel 210, and a subtractor
212.
[0025] FIG. 2 also shows various disturbances that are often
present in typical tape drive systems (e.g., shocks, vibrations,
stack shifts, and narrowband disturbances). FIG. 2 further shows a
reference signal r(t), which is the reference signal associated
with, for example, the centerline of the servo marks 116 of FIG. 1
to which the servo read head 208 should be tracking, a position
error signal (PES) e(t), and a control signal, u.sub.control, a
signal s(t) provided by the servo read head 208 to the servo
channel 210, a tape velocity estimate signal v(t), and a lateral
position estimate signal y(t). PES e(t) corresponds to the
difference between reference signal r(t) and lateral position
estimate signal y(t).
[0026] With regard to FIG. 1, the actuator 204 and the head module
206 correspond generally to the tape head actuator 102, and the
servo read head 208 corresponds to the servo read heads 104. The
servo channel 210 may be implemented, for example, as a
processor/microprocessor with microcode instructions stored either
inside servo channel 210 or in a separate EPROM (not shown), or as
a field-programmable gate array (FPGA), or as an
application-specific integrated circuit (ASIC), or as a combination
of the foregoing, or any other computing device capable of
performing the functionality required in embodiments of the present
disclosure.
[0027] In some embodiments, during operation(s), the servo control
system 200 uses the PES e(t) as an input to the PID controller 202.
The PID controller 202 outputs control signal u.sub.control to the
actuator 204. Based on the control signal u.sub.control, the
actuator 204 adjusts the position of the head module 206, which in
turn determines the position of the servo read head 208 and
corresponding read/write heads (not shown). The read/write heads
are maintained at a desired "on track" position via motion of the
actuator 204 and also via feedback provided by the servo read head
208. Specifically, the servo read head 208 provides a signal s(t)
to the servo channel 210. The servo channel 210 processes the
signal s(t) to generate a lateral position estimate signal y(t) and
a tape velocity estimate signal v(t), which indicates an estimate
of the longitudinal velocity of the tape being read/written.
Lateral position estimate signal y(t) along with reference signal
r(t) is input to the subtractor 212, which outputs the PES
difference signal e(t).
[0028] In the embodiments shown in FIGS. 1 and 2, the actuator 204
typically experiences vibrational resonances that is controlled.
The mechanical behavior of the actuator 204 may be approximated by
a simple spring-damper-mass model. As is known in the art, a
state-space form of the differential equations representing a
spring-damper-mass model is as follows:
[ d .times. y d .times. t d 2 .times. y d .times. t ] = [ 0 1 - k m
- c m ] .function. [ y d .times. y d .times. t ] + [ 0 0 K .times.
f C .times. f ] .function. [ z - y d .times. z d .times. t - d
.times. y d .times. t ] ##EQU00001##
[0029] It is noted that in the equation presented above, all
elements are known, except for z-y, and
d .times. z d .times. t - d .times. y d .times. t .
##EQU00002##
[0030] In the equation, m is the mass of the tape head actuator 102
in kilograms, including any additional mass attributed to, for
example, head cables and servo motors to be overcome when
accelerating the tape head actuator 102 in the Y direction; k is
the mechanical spring rate of the tape head actuator 102 in the Y
direction, in Newtons per meter; and c is the mechanical damping
experienced by the tape head actuator 102 in the Y direction, in
Newton-seconds per meter. Additionally, Kf is the feedback
coefficient with units of seconds.sup.-2 and Cf is the feedback
coefficient with units of second.sup.-1.
[0031] Referring now to FIG. 3A, illustrated is a frame 300 of a
timing-based-servo pattern, in accordance with embodiments of the
present disclosure. In some embodiments, the timing-based-servo
pattern includes the servo marks 302, 304, 306, and 308. It is
noted that the timing-based-servo pattern depicted in frame 300 is
the M-pattern discussed throughout the present disclosure and is
depicted with servo marks 302, 304, 306, and 308 for ease of
understanding. It should be further noted however, the
timing-based-servo pattern may be the 5-5-5-5 or 5-5-4-4 M-patterns
discussed in the present disclosure. In some embodiments, from the
timing-based-servo pattern found in frame 300, the terms z-y,
and
d .times. z d .times. t - d .times. y d .times. t ##EQU00003##
as discussed in regard to FIG. 2 can be derived from the relative
timing of pulses generated by a servo read head, such as one of the
servo read heads 104 reading the servo pattern, such as the servo
pattern 118 in FIG. 1.
[0032] In some embodiments, the frame 300 comprises two sets of
parallel servo marks: servo marks 302, 306 and servo marks 304,
308, with each set of servo marks 302, 306 and 304, 308 having
equal azimuth angles 310A-D to the servo mark centerline X (e.g.,
denoted as X to indicate the longitudinal X direction and with each
servo mark 302-308 respectively crossing the servo mark centerline
X at points A-D) of the timing-based-servo mark but opposite to the
other set, and which no servo marks 302, 304, 306, or 308 cross
each other. Although for ease of explanation the azimuth angles
310A-D are stated with respect to the servo mark centerline X, any
parallel to the servo mark centerline X can be used.
[0033] In FIG. 3A, frame 300 comprises parallel servo marks 302 and
306, each respectively having an equal azimuth angle 310A and 310B,
which for the purposes of this disclosure are which are 45-degrees
with respect to the servo mark centerline X; and parallel servo
marks 304 and 308, having an equal azimuth angle 310C and 310D,
which again for the purposes of this disclosure are which are
45-degrees with respect to the servo mark centerline X, but in the
opposite direction as the azimuth angles 310A and 310B.
[0034] In the arrangement shown in FIG. 3A, parallel servo marks
302 and 306 are interleaved with parallel servo marks 304 and 308,
forming a double chevron, or "M" shape/pattern. Again it is noted
that multiple servo marks could be interleaved between the servo
mark pairs 302, 306 and 304, 308, which would form the 5-5-5-5 or
5-5-4-4 M-patterns discussed in the present disclosure.
[0035] Referring now to FIG. 3B, illustrated is the frame 300 of a
timing-based-servo pattern demonstrating tape-creep, in accordance
with embodiments of the present disclosure. It is noted that like
reference numerals are used to designate like parts in the
accompanying drawings and that the frame 300 depicted in FIG. 3B is
the same, or substantially similar to, the frame 300 depicted in
FIG. 3A. It is further noted that the frame 300 in FIG. 3B now
includes skew angles 312, 314, a trajectory angle 316, and a servo
head trajectory 318.
[0036] Servo head trajectory 318 represents, for example, the path
over servo pattern frame 300 that a servo head 104 would follow
when tape 112 is experiencing movement in the lateral Y direction
as it moves in the longitudinal X direction. For the purposes of
this disclosure, servo head trajectory 318 forms, with the
longitudinal X direction, a positive angle 316, which may
colloquially be denoted as a. Due to the servo head trajectory 318,
being off from the centerline X as depicted in FIG. 3A, the azimuth
angles 310A-D distort in a shear distortion angle, which is denoted
as that indicates the timing-based-servo moving in/out of the
lateral Y direction. Thus, the azimuth angles 310A-D are no longer
at 45-degrees and are depicted as azimuth angles 310A'-D', with
azimuth angles 310A' and 310B' now being the angles derived from
.eta.+ (e.g., the original 45-degrees plus the inclusion of shear
distortion) and azimuth angles 310C' and 310D' being angles derived
from .eta.- (e.g., the original 45-degrees minus the inclusion of
shear distortion).
[0037] Further, as illustrated, servo head trajectory 318 also
forms an angle 312 with parallel servo marks 302, 306, and an angle
314 with parallel servo marks 304, 308. Angles 312 and 314 are
respectively .eta.-.alpha.+ (e.g., angle 312) and .eta.+.alpha.-
(angle 314). Servo head trajectory 318 continues to cross parallel
servo marks 302, 306 at points A' and B', respectively, and crosses
parallel servo marks 304, 308 at points C' and D',
respectively.
[0038] Parallel servo marks 302 and 306 are separated by a distance
of length d as measured from point A' to B' (e.g., segment A'B'),
and parallel servo marks 304 and 308 are separated by an equal
distance d as measured from point C' to D' (e.g., segment
C'D').
[0039] From the evaluation of the angles, segments, and distances
found within FIG. 3B, derivations can be performed/obtained by a
processor (e.g., in a tape drive, or by the tape drive itself) to
determine tape-creep of tape cartridge (e.g., the tape
media/magnetic tape within a tape cartridge). To begin:
d T .times. D ' - T .times. C ' = sin .function. ( .eta. + .alpha.
- .UPSILON. ) , and ##EQU00004## d T .times. B ' - T .times. A ' =
sin .function. ( .eta. - .alpha. + .UPSILON. ) , ##EQU00004.2##
where T refers to time (e.g., meaning TB' is the time at which the
tape head finishes reading or writing at point B' which is
subtracted by the time at which the tape head starts reading or
writing at point A', which would be finding the time it took the
tape head to read or write from distance d of segment A'B').
[0040] Combining the above equations to eliminate d, the equation
below is obtained:
T .times. D ' - T .times. C ' T .times. B ' - T .times. A ' = sin
.function. ( .eta. - .alpha. + .UPSILON. ) sin .function. ( .eta. +
.alpha. - .UPSILON. ) . ##EQU00005##
[0041] Further expanding the equation directly above:
T .times. D ' - T .times. C ' T .times. B ' - T .times. A ' = sin
.function. ( .eta. ) .times. cos .function. ( .alpha. - .UPSILON. )
- cos .function. ( .eta. ) .times. sin .function. ( .alpha. -
.UPSILON. ) sin .function. ( .eta. ) .times. cos .function. (
.alpha. + .UPSILON. ) + cos .function. ( .eta. ) .times. sin
.function. ( .alpha. - .UPSILON. ) ##EQU00006##
is obtained.
[0042] Now, the obtained equation is divided by cos(.alpha.-), to
obtain:
T .times. D ' - T .times. C ' T .times. B ' - T .times. A ' = 1 -
tan .function. ( .alpha. - .UPSILON. ) 1 + tan .function. ( .alpha.
- .UPSILON. ) ##EQU00007##
[0043] Then, further solving for tan(.alpha.-), the equation below
is obtained:
tan .function. ( .alpha. - .UPSILON. ) = ( T .times. B ' - T
.times. A ' ) - ( T .times. D ' - T .times. C ' ) ( T .times. B ' -
T .times. A ' ) + ( T .times. D ' - T .times. C ' )
##EQU00008##
[0044] From the equation directly above, the final equation to be
used by the processor to determine tape-creep can be obtained by
solving for (.alpha.-), in which case obtained is the .alpha.-
equation:
.alpha. - .UPSILON. = arctan .times. ( T .times. B ' - T .times. A
' ) - ( T .times. D ' - T .times. C ' ) ( T .times. B ' - T .times.
A ' ) + ( T .times. D ' - T .times. C ' ) ##EQU00009##
[0045] Where .alpha. is the trajectory of the magnetic tape over
the magnetic head and is the shear distortion angle of the magnetic
tape.
[0046] In some embodiments, the processor may utilize a method that
incorporates the .alpha.- equation presented above. In said method,
.alpha. (the trajectory, e.g., 318 of the tape over the magnetic
head) is separated from (the shear distortion angle of the tape).
In some embodiments, to separate .alpha. (trajectory of the tape
over the magnetic head) and (the shear distortion of the tape) is
to average .alpha.- over several M-patterns. This can be
accomplished because a will oscillate between positive and negative
values and the average .alpha. trajectory angle will necessarily be
zero, or close to zero. Thus, said averaging process will result in
an average , which will reveal the average shear distortion angle
of the tape.
[0047] In some embodiments, if the average reaches or exceeds a
shear distortion threshold, it indicates that the shear distortion
of the tape is causing tape creep, leading to a replacement of the
tape-media. Whereas, if the average is not over the shear
distortion threshold it indicates that the average .alpha.
trajectory angle is causing/will likely lead to tape creep, with
will lead to a realignment of the tape head.
[0048] In some embodiments, to find the average , a tape drive
(e.g., a processor in the tape drive, etc.) may calculate a slope
for each of the timing-based-servo marks in a timing-based-servo
group. The timing-based-servo marks may be arranged in one or more
M-patterns. The tape drive may average the slope for each of the
timing-based-servo marks across the one or more M-patterns. The
tape drive may generate a least-squares assessment of the averaged
slope. The tape drive may determine, from the least-squares
assessment, whether the averaged slope is demonstrative of
tape-creep. That is, the tape drive may determine, from the slopes
of servo marks 302-308 of FIG. 3B, that the servo marks 302-308
shifted since being presented in FIG. 3A, which may indicate that
the average shear distortion angle of the tape, , has shifted and
that tape-creep is may now be indicated for the frame 300.
[0049] In some embodiments, the tape drive detects the
timing-based-servo marks on the tape cartridge/magnetic tape of the
tape cartridge and the tape drive assembles, electronically, the
timing-based-servo marks into the one or more M-patterns. In some
embodiments, the timing-based-servo marks are written at a
45-degree angle relative to a servo mark of a magnetic media.
[0050] In some embodiments, the tape cartridge is a single-reel
tape cartridge that stores a tape-media and tape-creep is
determined for the tape-media stored in the single-reel tape
cartridge. In some embodiments, the tape cartridge is a dual-reel
cassette that stores a tape-media and tape-creep is determined for
the tape-media stored in the dual-reel tape cassette.
[0051] In some embodiments, the tape drive may record data in the
tape cartridge/on the tape-media in a parallel-serpentine pattern,
in which data is written to the tape in a parallel tracks in
lengthwise respect to the tape. In some embodiments, the tape drive
may record data in the tape cartridge/on the tape-media in a
helical-scan pattern, in which data is written to the tape (e.g.,
imprinted as data tracks on the tape) at an angle with respect to
the edge of the tape.
[0052] In some embodiments, to determine whether the averaged slope
is demonstrative of tape-creep, the tape drive compares the slope
against a threshold during a read operation. The tape drive
identifies that the threshold has been exceeded. The tape drive
reads all data from the tape cartridge and the tape drive transfers
all data to a second tape cartridge. For example, the tape drive
may compare the slope of the servo marks 302-308 of FIG. 3A, all of
which have (and ideally should have) slopes of 1, thus leading to
an average slope of 1, to that of the slopes of servo marks 302-308
of FIG. 3B. In FIG. 3B, the slopes of servo marks 302 and 306 may
be 1.5 and servo marks 304 and 308 may have slopes of 1.2, thus the
four servo marks 302-308 of FIG. 3B may have an average slope of
1.35.
[0053] The tape drive may compare the average slope of the servo
marks 302-308 of FIG. 3B to the ideal slope of 1 (of the servo
marks 302-308 of FIG. 3A) and determine that the change is that of
35%, the tape drive may determine from a predetermined threshold
that a tape-media indicating an average slope equal to or exceeding
of 33% is demonstrating severe average shear distortion angle of
the tape , which is indicative of tape-creep. The tape drive will
then perform data saving measures by reading all data from the
tape-media and transferring said tape to a second tape-media (e.g.,
magnetic tape) that is not demonstrating tape-creep.
[0054] In some embodiments, the tape drive may alert a user, with
an indication (e.g., a beep, a message, etc.) that the threshold
has been exceeded (or met).
[0055] In some embodiments, a second method may be used that
incorporates the .alpha.- equation. In said second method, no
effort is taken to separate .alpha. (e.g., the trajectory angle of
the tape over the magnetic head) and (e.g., the shear distortion
angle of the tape).
[0056] If the measured trajectory angle and shear distortion angle
.alpha.- is greater than a preselected threshold, then the data
contents of the distorted magnetic tape can be moved to a new,
suitable magnetic tape/tape cartridge before the data becomes
unreadable on the distorted magnetic tape, regardless of whether
trajectory angle .alpha. or shear distortion angle is at fault.
[0057] In some embodiments, a tape drive may calculate slopes for
three successive timing-based-servo marks in a timing-based-servo
group. The timing-based-servo marks may be arranged in one or more
M-patterns and the three successive timing-based-servo marks may be
across the one or more M-patterns. The tape drive may perform a
parabolic fit of a gradient of the slopes. The tape drive may
determine whether the gradient is demonstrative of tape-creep. In
some embodiments, the gradient may be determined/identified by the
equation:
( [ 3 .times. S .times. l .times. o .times. p .times. e 1 ] - [ 4
.times. S .times. 1 .times. o .times. p .times. e 2 ] + [ S .times.
l .times. o .times. p .times. e 3 ] ) 2 . ##EQU00010##
[0058] For example, the tape drive may find the slope of servo
marks 302-306 of FIG. 3B (or in some embodiments, three successive
servo marks of 116A or 116B). The tape drive may then determine a
gradient from the servo marks and perform a parabolic fit of the
gradient, which will indicate the distortion in both the x and y
directions of the servo marks, which respectively correlate to the
trajectory angle .alpha. or shear distortion angle . Regardless of
whichever angle, e.g., the trajectory angle .alpha. or shear
distortion angle , is larger, if the gradient exceeds a
predetermined/preselected threshold, the tape drive will deem the
tape-media with the servo-marks as demonstrating tape-creep and
issuing data saving operations.
[0059] In some embodiments, one such data saving operation may
include terminating the write operation of the tape drive before
existing data can be overwritten. That is, when determining that
the gradient is demonstrative of tape-creep, the tape drive may
compare the gradient against a threshold during a write operation.
The tape drive may identify that the threshold has been exceeded
and the tape drive may terminate the write operation before
existing data can be overwritten. This is because if tape-creep is
determined, the tape drive could write data in the wrong location
as the tape-media is distorted and thus information not meant to be
overwritten could be overwritten.
[0060] In some embodiments, in regard to thresholds, there are two
preselected thresholds, one for when a tape drive system is writing
to magnetic tape and one for when the tape drive system is reading
from the magnetic tape. During write operations, a write threshold
is used, which is more restrictive and rigid compared to a read
threshold that will be discussed in more depth below. During the
write operations, a WRITE_VERIFY process is used, which allows the
tape drive system to read the data immediately after it is written
to the magnetic tape. The tape drive system determines if the data
is written properly to the magnetic tape. If the tape drive detects
a write threshold number of inconsistencies/unreadable data on the
magnetic tape immediately after being written to, the tape drive
system will alert a user that a new magnetic tape is needed, or, in
some embodiments, the tape drive system will automatically begin
transferring data over from the magnetic tape to another magnetic
tape in the tape drive system.
[0061] During read operations, a normal READ process is used, which
allows the tape drive system to read the data is was instructed to
read. The tape drive system determines if the data is written
properly to the magnetic tape. If the tape drive then determines if
it detects a read threshold number of unreadable data on the
magnetic tape, the tape drive system will alert a user that a new
magnetic tape is needed, or, in some embodiments, the tape drive
system will automatically begin transferring data over from the
magnetic tape to another magnetic tape in the tape drive
system.
[0062] In some embodiments, the read threshold is less restrictive
than the write threshold (e.g., the read threshold allows for more
inconsistencies/unreadable data on the magnetic tape) because
reading from the tape does not involve likely writing over and
losing data as can happen with write operations. Further, the less
restrictive write threshold can allow for cartridge interchange
between tape drives, e.g., the tape drive system is allowed to
finish reading all data it was instructed to before initiating
mitigating/data saving operations (e.g., transferring of the data
from one magnetic tape/tape cartridge to another magnetic tape/tape
cartridge).
[0063] In some embodiments, a third method may be used that
converts the time-domain data of the .alpha.- equation to frequency
domain data. In said third method, a Fast Fourier Transform (FFT)
is employed over several (5-5-4-4) M-patterns to separate .alpha.
(e.g., the trajectory angle of the tape over the magnetic head) and
(e.g., the shear distortion angle of the tape). With the separation
of .alpha. and , one is able to determine, from a preselected
.alpha. threshold and/or a preselected threshold whether .alpha.
and/or is causing tape-creep (e.g., whether tape-creep is being
caused by the trajectory of the tape over the magnetic head and/or
the shear distortion of the tape).
[0064] In some embodiments, a tape drive may arrange the
timing-based-servo marks into a timing-based-servo pattern. The
timing-based-servo pattern is at least one M-pattern (e.g., the
5-5-4-4 M-pattern). The tape drive may select the at least one
M-pattern. The tape drive may match at least two timing-based-servo
marks in the at least one M-pattern. The tape drive may determine,
from the matching, whether an alignment of the at least two
timing-based-servo marks is demonstrative of tape-creep. In some
embodiments, due to the FFT nature of the third method, the
alignment is determined from found oscillations, movements, which
is discussed more fully below.
[0065] In some embodiments, the timing-based-servo pattern may
include a first set of servo marks that include five consecutive
angled lines directed toward a midway of the timing-based-servo
pattern and which touch a second set of servo marks. The second set
of servo marks include five consecutive angled lines directed away
from the midway of the timing-based-servo pattern and which touch a
third set of servo marks. The third set of servo marks include five
consecutive angled lines directed away from the midway of the
timing-based-servo pattern and which touch a fourth set of servo
marks, and the fourth set of servo marks include five consecutive
angled lines directed toward the midway of the timing-based-servo
pattern. In some embodiments, the timing-based-servo pattern is
from a European Computer Manufacturers Association (ECMA)-319 tape
cartridge.
[0066] In some embodiments, the third method discussed starts by
using the FFT to convert time-domain data into frequency domain
data. By use of the FFT of the .alpha.- equation and the complex
conjugate of the FFT, the power spectrum is calculated.
[0067] The components of .alpha. (e.g., the trajectory of the tape
over the magnetic head) is identified in the power spectrum to help
isolate (e.g., the shear distortion of the tape), which can
identify one of three things listed below.
[0068] One, tape vibration that is due to any idlers in the tape
path, which would be found at:
[0069] .omega..sub.IDLER=V/R.sub.IDLER, where .omega..sub.IDLER is
the angular frequency of an idler, V is the recording velocity of
the tape, and R.sub.IDLER is the idler radius.
[0070] If .omega..sub.IDLER is found to be above an angular
frequency threshold, it indicates that , the shear distortion of
the tape is too high, and is likely damaging the integrity of the
tape to properly be store data (e.g., be written to/read from)
because the idlers are distorting the alignment of the servo marks
discussed above.
[0071] Two, tape vibration due to each tape reels (e.g., of a
dual-reel tape cassette) can be found and would be found at:
[0072] .omega..sub.Supply-Reel=V/R.sub.supply-Reel and
.omega..sub.Takeup-Reel=V/R.sub.Takeup-Reel, where
.omega..sub.Supply-Reel is the angular frequency of a supply reel,
.omega..sub.Takeup-Reel is the angular frequency of a take-up reel,
and where R.sub.supply-Reel and R.sub.Takeup-Reel are the
respective radii of the outer wraps of tape.
[0073] If .omega..sub.Supply-Reel and/or .omega..sub.Takeup-Reel
are found to be above respective angular frequency thresholds, it
indicates that , the shear distortion of the tape is too high, and
is likely damaging the integrity of the tape to properly be store
data (e.g., be written to/read from).
[0074] Thirdly, longitudinal oscillations in a tape path can
manifest themselves in changes in the trajectory angle, .alpha..
The equation for longitudinal oscillation (e.g., .omega. that is
angular frequency) in a reel-to-reel tape path incorporates tape
vibration due to the spring-rate "k" of the magnetic tape and the
mass moment of inertia "I" of each tape reels, the equation thus
being represented as:
.omega. = { k .times. [ R Supply - Ree1 2 I Supply - Ree1 2 + R T
.times. a .times. k .times. eup - Reel 2 I T .times. a .times. k
.times. eup - Reel 2 ] } ##EQU00011##
[0075] where k=EA/L,
[0076] E=Young's Modulus of Magnetic Tape,
[0077] A=Cross-sectional area of Magnetic Tape,
[0078] L=Length of Tape; and where
[0079] R.sub.Supply-Reel and R.sub.Takeup-Reel are the respective
radii of the outer wraps of tape, and
[0080] I.sub.Supply-Reel and I.sub.Takeup-Reel are the respective
mass moments of inertial of the supply and take-up reels.
[0081] Thus, if .omega. is found to be above an oscillation
threshold, it indicates that .alpha., the trajectory angle of the
tape over the magnetic head is too high, and is likely causing the
tape head to not accurately read from and/or write to the tape due
to non-alignment.
[0082] It is noted that the frequencies associated with isolate
(the shear distortion of the tape) are likely to be much lower than
the frequencies associated with trajectory angle .alpha.. Thus, the
angular thresholds are likely to be relatively much higher than the
that of the oscillation threshold(s). It is further noted that all
or some of the methods discussed herein this disclosure are
contemplated to be used individually or in any combination of one
another.
[0083] Referring now to FIG. 4, illustrates a flowchart of an
example method 400 for averaging the slope of timing-based-servo
marks to determine tape-creep, in accordance with embodiments of
the present disclosure. In some embodiments, the method 400 may be
performed by a processor/microprocessor of a tape drive system or
by the tape drive system itself.
[0084] In some embodiments, the method 400 begins at operation 402,
where the processor calculates a slope for each timing-based-servo
mark in a timing-based-servo group. The timing-based-servo marks
are/have been arranged in one or more M-patterns. The method 400
proceeds to operation 404, where the processor averages the slope
for each of the timing-based-servo marks across the one or more
M-patterns.
[0085] The method 400 proceeds to operation 406, where the
processor generates a least-squares assessment of the averaged
slope. The method 400 proceeds to decision block 408, where the
processor determines, from the least-squares assessment, if the
averaged slope is demonstrative of tape-creep.
[0086] If, at decision block 408, the processor determines that the
averaged slope is not demonstrative of tape-creep, the method 400
proceeds to operation 410. At operation 410, the processor performs
normal operations of the tape drive system (e.g., reading/writing
of tape media). In some embodiments, after operation 410, the
method 400 ends. In some embodiments, after operation 410, the
method 400 continually repeats itself to ensure the tape drive
system can continue to perform normal operations.
[0087] If, however, at decision block 408, the processor determines
that the averaged slope is demonstrative of tape-creep, the method
400 proceeds to operation 412. At operation 412, the processor
performs data saving operations of the tape media being read
from/written to by the tape drive system. For example, the
processor can read all data from the tape media (e.g., in a tape
cartridge, etc.) and/or transfer all data to a second tape media
(e.g., on a second tape cartridge). In some embodiments, after
operation 412, the method 400 ends.
[0088] Referring now to FIG. 5, illustrates a flowchart of an
example method 500 for identifying the gradient of slopes for three
successive timing-based-servo marks to determine tape-creep, in
accordance with embodiments of the present disclosure. In some
embodiments, the method 500 may be performed by a
processor/microprocessor of a tape drive system or by the tape
drive system itself.
[0089] In some embodiments, the method 500 begins at operation 502,
where the processor calculates a slope for three successive
timing-based-servo marks in a timing-based-servo group. The
timing-based-servo marks are/have been arranged in one or more
M-patterns and the three successive timing-based-servo marks are
across the one or more M-patterns. The method 500 proceeds to
operation 504, where the processor performs a parabolic fit of a
gradient of the slopes.
[0090] The method 500 proceeds to decision block 506, where the
processor determines, from the parabolic fit, if the gradient is
demonstrative of tape-creep. If, at decision block 506, it is
determined that the gradient is not demonstrative of tape-creep,
the method 500 proceeds to operation 508.
[0091] At operation, 508 the processor performs normal operations
of the tape drive system (e.g., reading/writing of tape media). In
some embodiments, after operation 508, the method 500 ends. In some
embodiments, after operation 508, the method 500 continually
repeats itself to ensure the tape drive system can continue to
perform normal operations.
[0092] If, however, at decision block 506, the processor determines
that the gradient is demonstrative of tape-creep, the method 500
proceeds to operation 510. At operation 510, the processor performs
data saving operations of the tape media being read from/written to
by the tape drive system. For example, the processor can terminate
any write operations currently being conducted or set to be
conducted and/or the processor can alert a user that a new tape
media is needed in order to perform further write operations, etc.
In some embodiments, after operation 510, the method 500 ends.
[0093] Referring now to FIG. 6, illustrates a flowchart of an
example method 600 for arranging timing-based-servo marks to
determine tape-creep, in accordance with embodiments of the present
disclosure. In some embodiments, the method 600 may be performed by
a processor/microprocessor of a tape drive system or by the tape
drive system itself.
[0094] In some embodiments, the method 600 begins at operation 602,
where the processor arranges (e.g., logically, digitally, etc.) the
timing-based-servo marks into a timing-based-servo pattern. The
timing-based-servo pattern is at least one M-pattern. The method
600 proceeds to operation 604, where the processor selects the at
least one M-pattern.
[0095] The method 600 proceeds to operation 606, where the
processor matches (e.g., compares, aligns, etc.) at least two
timing-based-servo marks in the at least one M-pattern. The method
600 proceeds to decision block 608, where it is determined if the
alignment of the at least two timing-based-servo marks is
demonstrative of tape-creep.
[0096] If, at decision block 608, the processor determines that the
alignment is not demonstrative of tape-creep, the method 600
proceeds to operation 610. At operation 610, the processor performs
normal operations of the tape drive system (e.g., reading/writing
of tape media). In some embodiments, after operation 610, the
method 600 ends. In some embodiments, after operation 610, the
method 600 continually repeats itself to ensure the tape drive
system can continue to perform normal operations.
[0097] If, however, at decision block 608, the processor determines
that the alignment is not demonstrative of tape-creep, the method
600 proceeds to operation 612. At operation 612, the processor
performs data saving operations of the tape media being read
from/written to by the tape drive system. For example, the
processor can read all data from the tape media (e.g., in a tape
cartridge, etc.) and/or transfer all data to a second tape media
(e.g., on a second tape cartridge). In some embodiments, after
operation 612, the method 600 ends.
[0098] It is noted that the flowchart and block diagrams 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
disclosure. In this regard, each block in the flowchart or block
diagrams may represent a module, segment, or portion of
instructions, which comprises one or more executable instructions
for implementing the specified logical function(s). In some
alternative implementations, the functions noted in the blocks may
occur out of the order noted in the Figures. For example, two
blocks shown in succession may, in fact, be accomplished as one
step, executed concurrently, substantially concurrently, in a
partially or wholly temporally overlapping manner, 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 carry out combinations
of special purpose hardware and computer instructions.
[0099] The descriptions of the various embodiments of the present
disclosure have been presented for purposes of illustration, but
are not intended to be exhaustive or limited to the embodiments
disclosed. Many modifications and variations will be apparent to
those of ordinary skill in the art without departing from the scope
and spirit of the described embodiments. The terminology used
herein was chosen to best explain the principles of the
embodiments, the practical application or technical improvement
over technologies found in the marketplace, or to enable others of
ordinary skill in the art to understand the embodiments disclosed
herein.
[0100] Although the present disclosure has been described in terms
of specific embodiments, it is anticipated that alterations and
modification thereof will become apparent to the skilled in the
art. Therefore, it is intended that the following claims be
interpreted as covering all such alterations and modifications as
fall within the true spirit and scope of the disclosure.
* * * * *