U.S. patent application number 15/154010 was filed with the patent office on 2017-11-16 for heat-assisted shingled magnetic recording with variable track widths.
The applicant listed for this patent is Seagate Technology LLC. Invention is credited to Alfredo Chu, Edward Gage, Steven Granz, Wenzhong Zhu.
Application Number | 20170330591 15/154010 |
Document ID | / |
Family ID | 60295431 |
Filed Date | 2017-11-16 |
United States Patent
Application |
20170330591 |
Kind Code |
A1 |
Granz; Steven ; et
al. |
November 16, 2017 |
HEAT-ASSISTED SHINGLED MAGNETIC RECORDING WITH VARIABLE TRACK
WIDTHS
Abstract
A storage device includes a storage controller configured to
operate a heat-assisted magnetic recording head to write data to a
band of consecutive data tracks in a consecutive track order while
selectively alternating a power level of the heat source when
writing to some data tracks of the band.
Inventors: |
Granz; Steven; (Shakopee,
MN) ; Gage; Edward; (Lakeville, MN) ; Chu;
Alfredo; (Prior Lake, MN) ; Zhu; Wenzhong;
(Apple Valley, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seagate Technology LLC |
Cupertino |
CA |
US |
|
|
Family ID: |
60295431 |
Appl. No.: |
15/154010 |
Filed: |
May 13, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11B 7/126 20130101;
G11B 7/1267 20130101; G11B 7/1263 20130101; G11B 2005/0021
20130101; G11B 5/6088 20130101; G11B 2020/1238 20130101; G11B
20/1217 20130101; G11B 5/012 20130101 |
International
Class: |
G11B 7/1263 20120101
G11B007/1263; G11B 7/126 20120101 G11B007/126; G11B 20/12 20060101
G11B020/12 |
Claims
1. A system comprising: a storage medium; a heat-assisted magnetic
recording (HAMR) head with a heat source; and a storage device
controller configured to operate the HAMR head to write data to a
data band of consecutive data tracks in a consecutive track order
while dynamically altering a power level of the heat source to
write the data to some data tracks of the data band, wherein the
data band includes a first series of alternating data tracks and a
second series of alternating data tracks interlaced with the first
series, and each data track of the first series overlaps a
previously-written track by a first offset and each data track of
the second series overlaps a previously-written track by a second
offset different than the first offset.
2. The system of claim 1, wherein the storage device controller is
configured to alternate a power level of the heat source for data
writes to alternating data tracks in the data band.
3. The system of claim 1, wherein the storage device controller is
further configured to write data of a first linear density to the
first series of alternating tracks in the data band and to write
data of a second linear density to the second series of alternating
data tracks in the data band.
4. (canceled)
5. (canceled)
6. The system of claim 1, wherein data tracks of the data band are
arranged according to a uniform track pitch.
7. The system of claim 1, wherein the data band of consecutive data
tracks is a shingled data band in a shingled magnetic recording
system.
8. The system of claim 1, wherein all data tracks of the data band
have a substantially uniform effective track width.
9. A method comprising: receiving an instruction to write data to a
data band of consecutive data tracks on the storage medium
according to a consecutive track order; and executing the
instruction by writing the data to the data band according to the
consecutive track order while dynamically altering a power level of
the heat source to write data to some data tracks in the data band,
wherein the data band includes a first series of alternating data
tracks and a second series of alternating data tracks interlaced
with the first series, and each data track of the first series
overlaps a previously-written track by a first offset and each data
track of the second series does not overlap any previously-written
data track.
10. The method of claim 9, wherein executing the instruction
further comprises: alternating a power level of the heat source for
data writes to alternating data tracks in the data band.
11. The method of claim 9, further comprising: writing data of a
first linear density to the first series of alternating tracks in
the data band and writing data of a second linear density to the
second series of alternating data tracks in the data band.
12. (canceled)
13. (canceled)
14. The method of claim 9, wherein data tracks of the data band are
arranged according to a uniform track pitch.
15. The method of claim 9, wherein the data band of consecutive
data tracks is a shingled data band in a shingled magnetic
recording system.
16. The method of claim 9, wherein all data tracks of the data band
have a substantially uniform effective track width.
17-20. (canceled)
Description
BACKGROUND
[0001] Consumer demand drives continuing innovation of storage
devices of decreasing size and increased storage capacity. In the
case of disc-based storage mediums, the term areal density
capability (ADC) may refer to a product of a number of data tracks
on a disk (e.g., tracks per inch (TPI)) and a number of data bits
along each data track (e.g., bits per inch (BPI)). The tracks per
inch value is sometimes referred to as "radial density," while the
bits per inch value may be referred to as the "recording density,"
"bit density," or "linear density." As TPI and BPI values increase,
read heads have greater difficulty accurately reading data from the
data tracks, resulting in a higher bit error rate (BER). If the BER
becomes too high, storage device performance may suffer as error
correction and read retry operations are performed. Therefore, some
data storage devices are configured with preset TPI and BPI values
selected to achieve a high ADC while maintaining an acceptable BER.
A number of challenges are associated with increasing drive TPI and
BPI beyond current limits.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0002] FIG. 1 illustrates an example data storage device including
a transducer head assembly for writing data on a magnetic storage
medium.
[0003] FIG. 2 illustrates example techniques for selectively
altering heat source power of a heat-assisted magnetic recording
(HAMR) head to increase areal density capacity (ADC) in a shingled
magnetic recording system.
[0004] FIG. 3 illustrates further example techniques for
selectively altering heat source power of a HAMR head to increase
ADC in a shingled magnetic storage system.
[0005] FIG. 4 illustrates still further example techniques for
selectively altering power of a heat source power to increase ADC
in a shingled magnetic storage system.
[0006] FIG. 5 illustrates example operations for selectively
altering power of a HAMR head heat source to increase ADC on a
magnetic storage medium in a shingled magnetic storage system.
[0007] FIG. 6 illustrates example operations for selectively
altering power of a HAMR head heat source when writing to a last
data track of a shingled data band on a storage medium.
SUMMARY
[0008] One implementation of the disclosed technology provides a
storage controller that operates a heat-assisted magnetic recording
(HAMR) head to write data to a band of consecutive data tracks in a
consecutive track order while dynamically altering a heat source
power level of the HAMR head when writing to some data tracks in
the band. According to one implementation, the storage device
controller is configured to alternate a power level of the heat
source for data writes to each alternating data track in the band.
According to another implementation, the storage device controller
reduces the heat source power level when writing to a last data
track in the band as compared to the heat source power level used
for writing data to other data tracks in the band.
[0009] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This Summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used to limit the scope of the claimed
subject matter. These and various other features and advantages
will be apparent from a reading of the following Detailed
Description.
DETAILED DESCRIPTION
[0010] FIG. 1 illustrates a data storage device 100 including a
transducer head assembly 120 for writing data on a magnetic storage
medium 108. Although other implementations are contemplated, the
magnetic storage medium 108 is, in FIG. 1, a magnetic storage disk
on which data bits can be recorded using a magnetic write element
(not shown) and from which data bits can be read using a
magnetoresistive element (not shown). As illustrated in View A, the
magnetic storage medium 108 rotates about a spindle center or a
disk axis of rotation 112 during rotation, and includes an inner
diameter 104 and an outer diameter 102 between which are a number
of concentric data tracks 110. Information may be written to and
read from data bit locations in the data tracks on the magnetic
storage medium 108.
[0011] The transducer head assembly 120 is mounted on an actuator
assembly 109 at an end distal to an actuator axis of rotation 114.
The transducer head assembly 120 flies in close proximity above the
surface of the magnetic storage medium 108 during disk rotation.
The actuator assembly 109 rotates during a seek operation about the
disk axis of rotation 112. The seek operation positions the
transducer head assembly 120 over a target data track for read and
write operations. During a write operation, a write element (not
shown) of the transducer head assembly 120 converts a series of
electrical pulses sent from a controller 106 into a series of
magnetic pulses of commensurate magnitude and length, and the
magnetic pulses selectively magnetize magnetic grains of the
magnetic storage medium 108 as they pass below the transducer head
assembly 120.
[0012] In one implementation, the write element is a heat-assisted
magnetic recording (HAMR) head including a write pole, a heat
source (e.g., a laser), a waveguide, and a near-field transducer
(NFT). Heat (e.g., light) from the laser is directed through the
waveguide and focused onto the storage medium 108 by the NFT at a
location concurrently subjected to a magnetic pulse generated by
the write element. This process allows for a selective lowering of
the magnetic coercivity of the grains of the storage medium 108 in
a tightly focused area of the storage medium 108 that substantially
corresponds to an individual data bit. The heated region is encoded
with the recorded data bit based on the polarity of the applied
magnetic write field. After cooling, the magnetic coercivity
substantially returns to its pre-heating level, thereby stabilizing
the magnetization for that data bit. This write process is repeated
for multiple data bits on the storage medium, and such data bits
can be read using a magneto-resistive read head.
[0013] In FIG. 1, the controller 106 includes (or is
communicatively coupled to) a heat source power variation module
116. The heat source power variation module 116 controls settings
of HAMR head heat source on the transducer head assembly 120 to
selectively increase or decrease a power of the HAMR heat source
based on a location of a data track receiving data of a write
operation.
[0014] Increasing power of a heat source widens an area on the
storage medium 108 passing below the HAMR head heat source and
write element that may be magnetically polarized (e.g., flipped) by
magnetic pulses emitted by the HAMR head. This area is also
referred to herein as the "magnetic footprint" of the write
element. Stated differently, increasing heat source power while
operating the writer to write data has the effect of widening a
target data track in a cross track (CT) direction while decreasing
the heat source power during a write operation to a target data
track has the effect of narrowing a target data track in the
cross-track (CT) direction.
[0015] When data tracks are made wider by increasing the heat
source power, a maximum linear density, or the density of data bits
arranged in the down-track (DT) direction, can be increased as
compared to a maximum linear density of narrow data tracks while
maintaining an acceptable bit error rate. However, this linear
density is, in general, increased at the expense of track density.
That is, data tracks can be made wider in the cross-track direction
to accommodate more bits in the down-track direction but widening
the data tracks, in turn, decreases a total number of data tracks
that can fit on the storage medium 108.
[0016] Another competing concern that imposes limits on attainable
areal density capacity is adjacent track interference (ATI). ATI
refers to degradation of stored data that may occur on one data
track over time due to repeated writes to an adjacent data track.
In general, as track density increases, ATI worsens. The herein
disclosed data write and management techniques alleviate some
limitations of ATI and boost attainable areal density capacity of
the storage medium 108 by intelligently manipulating track pitch,
track overlap, and track size via selective alteration of HAMR head
laser power in a shingled magnetic recording (SMR) system.
[0017] The following discussion details two example SMR data
management schemes employing the HAMR power variation module 116 to
improve recording capacity in a HAMR. It should be understood that
the example functions served by the HAMR power variation module 116
may also be useful in implementing a variety of other data
management schemes not discussed herein, including those with
applications in systems that do not utilize SMR.
[0018] As background, SMR is one way to decrease the size of data
cells on the magnetic storage medium 108 without a corresponding
decrease in the size of a writer on the transducer head assembly
120. In SMR systems, a magnetic field produced by the writer is
strong enough to affect two adjacent data tracks on the magnetic
storage medium 108 on a single pass of the writer. In other words,
a magnetic footprint (e.g., an area of the storage medium
magnetically polarized by the writer on a single pass) may be
defined to correspond to two different data tracks on the magnetic
storage medium 108.
[0019] For example, View B illustrates a data write by a HAMR head
having a magnetic footprint W1 that is defined to be equal in width
to a width of two data tracks combined (e.g., 132 and 134). An
initial write to the data track 132 incidentally magnetizes (e.g.,
corrupts) data on the adjacent data track 134. The corrupted data
in the data track 134 can be corrected on a subsequent pass of the
writer over the data track 134, but this data write to the data
track 134 in turn corrupts data on data track 136, and so on.
[0020] To manage data in this SMR system despite the
above-described overlap, data tracks on the data storage device 100
may be grouped into data bands (e.g., data bands 138, 140), where
each data band is separated from other adjacent data bands by one
or more guard tracks (e.g., guard tracks 152 and 154) where no data
is stored. In an example write operation of the data track 132, the
storage device 100 reads all data tracks in the associated data
band 138 (e.g., including data tracks 132, 134, 136, and 142) into
a memory location in a consecutive order. In memory, the data
storage device 100 updates the one or more data cells to be changed
by the write operation and then re-writes, in a consecutive track
order, the data tracks 132, 134, 136, and 142 including the one or
more updated cells.
[0021] Notably, the last data track in each of the data bands 138,
140 (e.g., the data track 142 in band 138 and data track 148 in
band 140) is adjacent to a guard track 152 or 154 and is not
overlapped by any other data track. Therefore, the last track of
each SMR data band is also referred to herein as the
"non-overlapped track." In some implementations, the HAMR power
variation module 116 selectively reduces HAMR heat source power
when writing to the non-overlapped track band in some or all data
bands, such as when writing to the non-overlapped the data track
148 in the data band 140). Such a reduction in HAMR heat source
power has the effect of reducing the written track width of the
non-overlapped track 148 from an amount W1 to an amount W2, as
further shown in View B. In addition, a center of the
non-overlapped data track 148 may be shifted toward the immediately
adjacent data track 146 such that an effective track width of the
data track 146 is equal or approximately equal to an effective
track width of the data track 148. As used herein, the term
"effective track width" refers to a width of a written data track
that is not overlapped by any other data track. Selectively
decreasing HAMR heat source power when writing to the
non-overlapped data track in some or all data bands, as described
above, makes more efficient use of space on the storage medium 108,
which in turn allows for an increase in a track density (e.g., the
total number of tracks per inch (TPI)).
[0022] In some implementations, the HAMR power variation module 116
does not selectively reduce HAMR heat source power when writing to
the non-overlapping data of a data band, as shown by the size of
the magnetic footprint W1 used to write all data tracks in the data
band 138. In this case, linear density (BPI) of the non-overlapping
data track may be increased as compared to a linear density of
other data tracks in a same data band.
[0023] View C illustrates data tracks of the magnetic storage
medium 108 storing data according to another SMR technique that
makes use of varied heat source power of the HAMR head. Like the
SMR technique of View B, data is written to the shingled bands 138,
140 according to a consecutive track order. For example, a write to
the band 138 entails a write to track 132, followed by a write to
track 134, followed by a write to track 136, and thereafter a write
to track 142. However, the controller 106 defines the center of
each track in a non-conventional manner such that there exists a
variable degree of overlap between different pairs of adjacent
tracks. For example, there is a substantially large overlap between
the regions magnetized in consecutive data writes to the data
tracks 132 and 134. In contrast, there is little or no overlap
between the regions magnetized in consecutive data writes to the
data tracks 134 and 136.
[0024] Benefits of this staggered overlap scheme are observed when
the HAMR power variation module 116 also varies a HAMR heat source
power when writing to alternating tracks in each of the data bands
(e.g., 138, 140). For example, a first higher HAMR heat source
power is used to write data to the tracks 132, 136, 144, and 148
and a second lower heat source power is used when writing data to
the tracks 134, 142, 146, etc. Linear density is selectively
increased when writing to some data tracks, such as those written
with the higher HAMR heat source power.
[0025] One benefit of this alternating wide/narrow written data
track scheme is that linear density can be increased on the wider
data tracks as compared to the narrow data tracks while still
maintaining an acceptable bit error rate. Thus, half of data tracks
on the storage medium 108 may be written at a higher linear density
than a linear density typical of a conventional SMR scheme. Another
benefit of this technique is attributable to the use of the
staggered (e.g., mismatched) track overlaps in conjunction with the
alternating wide/low written data track widths. Specifically, this
scheme facilitates a uniform increase in track pitch (e.g.,
center-to-center adjacent track spacing) as compared to
conventional SMR systems, without decreasing a total number of
tracks on the storage medium. This increase in the track pitch
further translates to a similar observable ATI as in conventional
SMR systems without a significant loss of track density or linear
density for data tracks written at an increased HAMR heat source
power. By combining this variable HAMR power scheme with the
illustrated SMR varied-track-overlap scheme, ADC can be
significantly improved as compared to other HAMR SMR systems that
use a constant HAMR power and track overlap.
[0026] The controller 106 includes software and/or hardware, and
may be implemented in any tangible computer-readable storage media
within or communicatively coupled to the data storage device 100.
The term "tangible computer-readable storage media" includes, but
is not limited to, RAM, ROM, EEPROM, flash memory or other memory
technology, CDROM, digital versatile disks (DVD) or other optical
disk storage, magnetic cassettes, magnetic tape, magnetic disk
storage or other magnetic storage devices, or any other tangible
medium which can be used to store the desired information and which
can accessed by mobile device or computer. In contrast to tangible
computer-readable storage media, intangible computer-readable
communication signals may embody computer readable instructions,
data structures, program modules or other data resident in a
modulated data signal, such as a carrier wave or other signal
transport mechanism. The term "modulated data signal" means a
signal that has one or more of its characteristics set or changed
in such a manner as to encode information in the signal.
[0027] FIG. 2 illustrates example techniques for selectively
altering power of a HAMR heat source to increase ADC on a magnetic
storage medium 200 in a shingled magnetic storage system. The
magnetic storage medium 200 includes a number of data tracks
organized into data bands (e.g., data bands 218 and 220) such that
each data band is separated from the immediately adjacent data band
by a guard track (e.g., guard tracks 222, 224) where no data is
stored.
[0028] Each of the data bands 218 and 220 includes a number of data
tracks (e.g., data tracks 202, 204, 206, 208, 210, 212, 214, and
216) written according to a consecutive track order. For example,
an update to data track 206 of the data band 218 may, in one
implementation, entail (1) reading data tracks 202, 204, 206 and
208 into memory; (2); within the memory, merging the new data of
track 206 in place of old data; and (3) re-writing the data tracks
202, 204, 206, and 208 from the memory.
[0029] Each of the data bands 218, 220 further includes data tracks
of two different alternating track widths. For example, a first
series of alternating data tracks 202 and 206 within the data band
218 have a first written track width that is wider than a second
written track width of interlaced data tracks 204 and 208 of the
data band 218. To achieve this variance in written track width, the
wider data tracks (e.g., 202, 206, 210, and 214) are written with a
HAMR heat source power set to a first power level while the
narrower data tracks (e.g., 204, 208, 212, and 216) are written
with the HAMR heat source power set to a second power level lower
than the first power level.
[0030] In addition, consecutive data tracks in FIG. 2 are unevenly
offset from one another such that there exist differing degrees of
overlap between consecutive data tracks. For example, each of the
narrower data tracks (e.g., the data tracks 204, 208, 212 and 216)
overlaps the immediately adjacent, previously-written data track by
the same amount, OL1, but each of the wider data tracks (e.g., the
data tracks 202, 206, 210, and 214) do not overlap the immediately
adjacent, previously-written data track at all. As a result of this
uneven track overlap scheme and the alternating wide/narrow written
track widths, track pitch (TP1) is uniform across the area shown on
the magnetic storage medium 208. For example, a center-to-center
distance TP1 is identical between each pair of adjacent data
tracks. In some implementations, the track pitch TP1 is uniform
across the entire surface of the storage medium 200; in other
implementations the track pitch TP1 is uniform within each of a
number of defined radial zones on the storage medium 200. Notably,
this uniform track pitch may be slightly larger than a track pitch
in an otherwise identical SMR system (e.g., same storage medium,
same TPI) where the data tracks in each data band are of identical
written width and placed according to a uniform overlap scheme.
This larger track pitch translates to a similar observable ATI as
compared to such a conventional SMR system without a loss in linear
density or track density.
[0031] In one implementation, the tracks 202 and 206 store data
bits of a higher linear density than the interlaced tracks 204 and
208. For example, a first heat source power may be optimized for
writing to the wider data tracks (e.g. 202, 206, 210, 214) at a
first linear density while a second heat source power may be
optimized for writing data to the narrower data tracks (e.g., 204,
208, 212, and 216) at a second linear density lower than the first
linear density. This dual linear density scheme for alternating
tracks provides for a total ADC that is higher than conventional
SMR systems employing uniform linear densities within each data
band.
[0032] FIG. 3 illustrates further example techniques for
selectively altering power of a HAMR heat source to increase ADC on
a magnetic storage medium 300 in a shingled magnetic storage
system. The magnetic storage medium 300 includes a number of data
tracks organized into data bands (e.g., data bands 318 and 320)
such that each data band is separated from the immediately adjacent
data band by a guard track (e.g., guard tracks 322, 324) where no
data is stored.
[0033] Each of the data bands 318 and 320 includes a number of data
tracks (e.g., data tracks 302, 304, 306, 308, 310, 312, 314, and
316) written according to a consecutive track order (e.g., as
indicated by the arrow labeled "Track write order" in FIG. 3). In
addition, each of the data bands 318, 320 includes data tracks of
altering track widths. For example, alternating data tracks 302 and
306 have a first written track width that is wider than a second
written track width of interlaced data tracks 304 and 308. To
achieve this variance in written track width, the wider data tracks
(e.g., 302, 306, 310, and 314) are written with a HAMR heat source
power set to a first power level while the narrower data tracks
(e.g., 304, 308, 312, and 316) are written with the HAMR heat
source power set to a second power level lower than the first power
level.
[0034] The placement of consecutive data tracks in FIG. 3 is
staggered so that there exist differing degrees of overlap between
each data track and the immediately adjacent previously-written
track. For example, the data track 304 overlaps the data track 302
by a first overlap amount (OL1), while the data track 306 overlaps
the data track 304 by a second overlap amount (OL2). In one
implementation, the first overlap amount OL1 is larger than the
second overlap amount OL2. As a result of this uneven track overlap
scheme including tracks of variable (e.g., wide v. narrow) written
widths, track pitch (TP1) is uniform across the area shown on the
magnetic storage medium 300. In some implementations, the track
pitch TP1 is uniform across the entire surface of the storage
medium 300; in other implementations the track pitch TP1 is uniform
within each of a number of defined radial zones on the storage
medium 300.
[0035] In one implementation, the wider written tracks (e.g., 302,
406, 310, and 312) store data bits of a higher linear density than
the narrow written tracks (e.g., 304, 308, 312, and 316). For
example, linear density may be optimized separately for the wider
data tracks (e.g. 302, 306, 310, 314) and the narrow data tracks
(e.g., 304, 308, 312, and 316) such that the wider data tracks are
written at a first, higher HAMR laser power and higher linear
density while the narrow data tracks are written at a second, lower
HAMR laser power and lower linear density. This dual linear density
scheme for alternating tracks provides for a total ADC that is
higher than conventional SMR systems employing uniform linear
densities within each data band.
[0036] FIG. 4 illustrates still further example techniques for
selectively altering power of a HAMR heat source to increase ADC on
a magnetic storage medium 400 in a shingled magnetic storage
system. The magnetic storage medium 400 includes a number of data
tracks organized into data bands (e.g., data bands 418 and 420)
such that each data band is separated from the immediately adjacent
data band by a guard track (e.g., guard tracks 422, 424) where no
data is stored. In operation, data tracks within each of the data
bands 418 and 420 are written according to a consecutive write
order, indicated by an arrow "Track write order" in FIG. 4.
[0037] In FIG. 4, a last data track in each of the data bands 418
and 420 has an effective track width approximately equal to an
effective track width of other data tracks in a same data band 418
or 420. In one implementation, this effect is generated by a
controller of the shingled magnetic storage system that selectively
decreases a HAMR heat source power when writing data to last data
track of each data band (e.g., data tracks 408 and 416). For
example, the shingled data tracks 402 and 404 are written while the
HAMR heat source power is set to allow the writer to generate a
magnetic footprint W1, while each of the non-overlapped data tracks
408 and 416 are written while the HAMR heat source power is set to
a lower power that allows the writer to generate a smaller magnetic
footprint W2.
[0038] In the illustrated implementation, a center of the last data
track in each data band 418 and 420 is shifted toward an adjacent
track in the same data band. For example, a data write to the last
data track 408 entails a reduction in the size of the magnetic
footprint of the writer from W2 to W1 and a shift in the center of
the data track 408 from a position C1 to C2 maintain a uniform or
substantially uniform center-to-center spacing between all adjacent
pairs of data tracks in the data bands 418 or 420, as shown by
track pitch indicator "TP1".
[0039] In other implementations, a track pitch may be inconsistent
within a data band. For example, a first data track and/or last
data track in a data band may be positioned to deliberately have a
different track pitch than other data tracks in the data band, as
disclosed in U.S. Pat. No. 8,867,161, which is hereby incorporated
by reference for all that it discloses or teaches.
[0040] Decreasing the HAMR heat source power to resize the last
data track in each data band, as shown, saves space on the magnetic
storage medium 400, allowing for the data bands to be placed closer
together. This results in a net increase in total TPI of the
magnetic storage medium 400.
[0041] To permit this decrease in effective track width of the last
data track of each shingled band, the controller may--in some
implementations--decrease the linear density (BPI) when writing to
the last data tracks 408 and 416 of the data bands 418 and 420,
respectively. In other cases, the last data tracks 408 and 416
store data of BPI equal to the BPI of data stored on other data
tracks of the corresponding data bans 418 or 420.
[0042] FIG. 5 illustrates example operations 500 for selectively
altering power of a HAMR heat source to increase ADC on a magnetic
storage medium in a shingled magnetic storage system. A receiving
operation 510 receives an instruction to write data to a target
data track in a shingled data band of and SMR system. A
determination operation 515 determines whether the target data
track is included within a first series of alternating data tracks
or a second series of alternating data tracks of the data band. In
one implementation, the first series of alternating data tracks
includes every other data track in the band (e.g., odd numbered
tracks) and the second series of alternating data tracks includes
the data tracks interlaced with the first series of alternating
data tracks (e.g., the even-numbered tracks).
[0043] If the determination operation 515 determines that the
target data track is included in the first series of alternating
data tracks, operations 520-530 are performed. A selection
operation 520 selects a first linear density for writing the data
to the target data track, and another selection operation 525
selects a first power level for operating a heat source of the HAMR
head (e.g., a laser) during a write to the target data track.
Subsequently, a write operation 530 writes the data to the target
data track at the first linear density while operating the heat
source at the first power level.
[0044] If, on the other hand, the determination operation 515
determines that the target data track is included in the second
series of alternating data tracks, operations 535-545 are
performed. A selection operation 535 selects a second linear
density for writing the data to the target data track, and another
selection operation 540 selects a second power level for operating
the heat source of the HAMR head during a write to the target data
track. Subsequently, a write operation 545 writes the data to the
target data track at the second linear density while operating the
heat source at the second power level. In one implementation, the
second linear density is higher than the first linear density and
the second power level is higher than the first power level.
[0045] In some implementations of the disclosed technology, a track
pitch is defined to be uniform for all data tracks in the data
band. Due to differing write track widths (e.g., on account of the
first and second laser powers), some data tracks in a data band may
overlap a directly adjacent, previously written data track by a
different degree than other data tracks. A few examples of this
staggered overlap concept are shown and described in greater detail
above with respect to FIGS. 2 and 3.
[0046] FIG. 6 illustrates example operations 600 for selectively
altering power of a HAMR heat source when writing data to a last
data track of a shingled data band on a storage medium. A receiving
instruction 605 receives an instruction to write data to a target
data track. A determination operation 610 determines if the target
data track is a last data track (e.g., a non-overlapping track) in
a shingled data band of an SMR system. The determination operation
610 may be performed, for example, by accessing a table stored in
firmware of the storage device and identifying a write current
parameter or a clearance parameter associated with the target data
track
[0047] If the target data track is a track in a shingled data band
but is not the last data track (e.g., the non-overlapping track) in
the data band, a selection operation 615 selects a first power
level for a HAMR heat source and a selection operation 620 selects
a first linear density. A write operation 625 then writes the data
at the first linear density to the target data track while
operating the heat source of a HAMR head at the first power level,
creating a data track of a first width.
[0048] If, on the other hand, the determination operation 610
determines that the target data track is the last data track in a
shingled data band, another selection operation 630 selects a
second power level for the HAMR heat source and another selection
operation 635 selects a second linear density. A write operation
640 then writes the data at the second linear density to the target
data track while operating the heat source of the HAMR head at the
second power level, creating a data track of a second width. In one
implementation, the second power level is lower than the first
power level, the second width is narrower than the first width, and
the second linear density is higher than the first linear density.
This reduction in track width of the last data track decreases
wasted space on the storage medium and allows for a net increase in
track density.
[0049] In some implementations, the last data track in a data band
is further positioned to have a center offset from a center of a
directly adjacent data track by an amount substantially equal to a
center-to-center spacing of all data tracks in the data band. For
example, the data band may have a substantially uniform track
pitch, and last data track in the data band may have an effective
track width equal to an effective track width of all other data
tracks in the data band.
[0050] The embodiments of the disclosed technology described herein
are implemented as logical steps in one or more computer systems.
The logical operations of the presently disclosed technology are
implemented (1) as a sequence of processor-implemented steps
executing in one or more computer systems and (2) as interconnected
machine or circuit modules within one or more computer systems. The
implementation is a matter of choice, dependent on the performance
requirements of the computer system implementing the disclosed
technology. Accordingly, the logical operations making up the
embodiments of the disclosed technology described herein are
referred to variously as operations, steps, objects, or modules.
Furthermore, it should be understood that logical operations may be
performed in any order, adding and omitting as desired, unless
explicitly claimed otherwise or a specific order is inherently
necessitated by the claim language.
[0051] The above specification, examples, and data provide a
complete description of the structure and use of exemplary
embodiments of the disclosed technology. Since many embodiments of
the disclosed technology can be made without departing from the
spirit and scope of the disclosed technology, the disclosed
technology resides in the claims hereinafter appended. Furthermore,
structural features of the different embodiments may be combined in
yet another embodiment without departing from the recited
claims.
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