U.S. patent application number 13/788502 was filed with the patent office on 2014-09-11 for power state change in disk drive based on disk access history.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. The applicant listed for this patent is KABUSHIKI KAISHA TOSHIBA. Invention is credited to Mine Wonkyung BUDIMAN, Eric R. DUNN, Richard M. EHRLICH, Annie Mylang LE, Daniel TCHEN, Fernando Anibal ZAYAS.
Application Number | 20140258745 13/788502 |
Document ID | / |
Family ID | 51489404 |
Filed Date | 2014-09-11 |
United States Patent
Application |
20140258745 |
Kind Code |
A1 |
EHRLICH; Richard M. ; et
al. |
September 11, 2014 |
POWER STATE CHANGE IN DISK DRIVE BASED ON DISK ACCESS HISTORY
Abstract
A data storage device that includes a magnetic storage device
selects one or more power states of the magnetic storage device
based on a time interval since a most recent time data has been
read from or written to the magnetic storage device. The power
state of the magnetic storage device can be changed from a higher
power consumption state to a lower power consumption state when the
time interval exceeds a predetermined value. The power consumption
state may be changed from an active servo state to an intermediate
power consumption state, a park state, and/or a standby state,
depending on the time elapsed since the most recent time data has
been read from or written to the magnetic storage device.
Inventors: |
EHRLICH; Richard M.;
(Saratoga, CA) ; DUNN; Eric R.; (Cupertino,
CA) ; TCHEN; Daniel; (San Jose, CA) ; LE;
Annie Mylang; (San Jose, CA) ; BUDIMAN; Mine
Wonkyung; (Livermore, CA) ; ZAYAS; Fernando
Anibal; (Rangiora, NZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOSHIBA |
Tokyo |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
51489404 |
Appl. No.: |
13/788502 |
Filed: |
March 7, 2013 |
Current U.S.
Class: |
713/320 |
Current CPC
Class: |
G06F 1/3228 20130101;
G06F 1/3268 20130101; Y02D 10/00 20180101; G06F 3/0653 20130101;
G06F 3/0676 20130101; Y02D 10/154 20180101; G06F 3/0625
20130101 |
Class at
Publication: |
713/320 |
International
Class: |
G06F 1/32 20060101
G06F001/32 |
Claims
1. A method of power management in a data storage device that
includes a magnetic storage device, the method comprising:
measuring a time interval since a most recent time data has been
read from or written to the magnetic storage device; and in
response to the time interval exceeding a predetermined value,
changing a current power consumption state of the magnetic storage
device to a lower power consumption state.
2. The method of claim 1, wherein the time interval measured is a
time interval since a most recent time data has been read from or
written to the magnetic storage device to satisfy a host
command.
3. The method of claim 2, wherein the current power consumption
state comprises an active servo state and the lower power
consumption state comprises an intermediate power consumption state
that uses less power than the active servo state and more power
than a parked state.
4. The method of claim 3, wherein the intermediate power
consumption state comprises a float state in which a servo system
of the magnetic storage device is not used to provide continuous
position control of a read/write head of the magnetic storage
device.
5. The method of claim 3, wherein the intermediate power
consumption state comprises a low-frequency servo state in which a
servo system of the magnetic storage device provides position
control of a read/write head of the magnetic storage device using
no more than a portion of the servo wedges on a storage disk of the
magnetic storage device.
6. The method of claim 1, wherein the current power consumption
state comprises an intermediate power consumption state that uses
less power than the active servo state and more power than a parked
state.
7. The method of claim 6, wherein the lower power consumption state
comprises one of a standby state in which a storage disk of the
magnetic storage device is not spinning and a parked state in which
a read/write head of the magnetic storage device is parked.
8. The method of claim 1, wherein the current power consumption
state comprises a parked state in which a read/write head of the
magnetic storage device is parked.
9. The method of claim 8, wherein the lower power consumption state
comprises a standby state in which a storage disk of the magnetic
storage device is not spinning.
10. The method of claim 1, further comprising, during the time
interval in which the magnetic storage device is not accessed:
receiving one or more commands; and satisfying the one or more
commands using at least one of a volatile solid-state memory of the
data storage device and a non-volatile solid-state memory device of
the data storage device.
11. A data storage device, comprising: a magnetic storage device;
and a controller configured to: measure a time interval since a
most recent time data has been read from or written to the magnetic
storage device; and in response to the time interval exceeding a
predetermined value, change a current power consumption state of
the magnetic storage device to a lower power consumption state.
12. The data storage device of claim 11, wherein the time interval
measured is a time interval since a most recent time data has been
read from or written to the magnetic storage device to satisfy a
host command.
13. The data storage device of claim 12, wherein the current power
consumption state comprises an active servo state and the lower
power consumption state comprises an intermediate power consumption
state that uses less power than the active servo state and more
power than a parked state.
14. The data storage device of claim 11, wherein the current power
consumption state comprises an intermediate power consumption state
that uses less power than the active servo state and more power
than a parked state.
15. The data storage device of claim 14, wherein the lower power
consumption state comprises one of a standby state in which a
storage disk of the magnetic storage device is not spinning and a
parked state in which a read/write head of the magnetic storage
device is parked.
16. The data storage device of claim 11, wherein the current power
consumption state comprises a parked state in which a read/write
head of the magnetic storage device is parked.
17. The data storage device of claim 16, wherein the lower power
consumption state comprises a standby state in which a storage disk
of the magnetic storage device is not spinning.
18. The data storage device of claim 11, wherein the controller is
further configured to, during the time interval in which the
magnetic storage device is not accessed: receive one or more
commands; and satisfy the one or more commands using one of a
volatile solid-state memory of the data storage device, a
non-volatile solid-state memory device of the data storage device,
and a combination of both.
19. A data storage device, comprising: a magnetic storage device; a
non-volatile solid-state device; and a controller configured to:
determine that a portion of the non-volatile solid-state device
used to store data that are not also stored on the magnetic storage
device is greater than a predetermined value; change a power state
of the magnetic storage device from an initial power state to an
active servo state, the initial power state being a lower power
state than the active servo state; and control the writing to the
magnetic storage device of at least a portion of the data that are
not also stored on the magnetic storage device.
20. The data storage device of claim 19, wherein the controller is
further configured to, while the magnetic storage device is at the
initial power state, control the writing of data from a host device
to the non-volatile solid-state device.
Description
BACKGROUND
[0001] Disk drives primarily store digital data in concentric
tracks on the surface of a data storage disk and are commonly used
for data storage in electronic devices. The data storage disk is
typically a rotatable hard disk with a layer of magnetic material
thereon, and data are read from or written to a desired track on
the data storage disk using a read/write head that is held
proximate to the track while the disk spins about its center at a
constant angular velocity. To properly align the read/write head
with a desired track during a read or write operation, disk drives
generally use a closed-loop servo system that relies on servo data
stored in servo sectors written on the disk surface when the disk
drive is manufactured.
[0002] Some operations in a disk drive use a significant amount of
energy, even when read or write commands are not being serviced by
the disk drive. For example, continuously spinning the data storage
disk requires approximately the same power whether or not read or
write commands are being performed. Similarly, actively controlling
read/write head position with the servo system involves performing
servo sampling, signal processing, and associated decoding with a
read channel, all of which utilize substantial computational
resources, independent of read or write commands. Because disk
drives are frequently used in portable electronic devices in which
available power is limited, such as laptop computers, restricting
such energy-intensive operations in a disk drive is generally
desirable.
SUMMARY
[0003] One or more embodiments provide systems and methods for
storing data in a data storage device that includes a magnetic
storage device. During operation, the data storage device selects
one or more power states of the magnetic storage device based on a
time interval since a most recent time data has been read from or
written to the magnetic storage device. Specifically, the power
state of the magnetic storage device can be changed from a higher
power consumption state to a lower power consumption state when the
time interval exceeds a predetermined value. For example, the power
consumption state may be changed from an active servo state to an
intermediate power consumption state, a park state, and/or a
standby state, depending on the time elapsed since a most recent
time data has been read from or written to the magnetic storage
device.
[0004] A method of power management in a data storage device that
includes a magnetic storage device comprises, according to one
embodiment, measuring a time interval since a most recent time data
has been read from or written to the magnetic storage device, and,
in response to the time interval exceeding a predetermined value,
changing a current power consumption state of the magnetic storage
device to a lower power consumption state.
[0005] According to another embodiment, a data storage device
comprises a magnetic storage device and a controller. The
controller is configured to measure a time interval since a most
recent time data has been read from or written to the magnetic
storage device, and, in response to the time interval exceeding a
predetermined value, change a current power consumption state of
the magnetic storage device to a lower power consumption state.
[0006] According to another embodiment, a data storage device
comprises a magnetic storage device, a non-volatile solid-state
device, and a controller. The controller is configured to determine
that a portion of the non-volatile solid-state device used to store
data that are not also stored on the magnetic storage device is
greater than a predetermined value, change a power state of the
magnetic storage device from an initial power state to an active
servo state, the initial power state being a lower power state than
the active servo state, and control the writing to the magnetic
storage device of at least a portion of the data that are not also
stored on the magnetic storage device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] So that the manner in which the above recited features of
the embodiments can be understood in detail, a more particular
description of the embodiments, briefly summarized above, may be
had by reference to the appended drawings. It is to be noted,
however, that the appended drawings illustrate only typical
embodiments and are therefore not to be considered limiting of its
scope, for there may be other equally effective embodiments.
[0008] FIG. 1 is a schematic view of an exemplary disk drive,
according to one embodiment.
[0009] FIG. 2 illustrates an operational diagram of a disk drive
with elements of electronic circuits shown configured according to
one embodiment.
[0010] FIG. 3 illustrates a power-state diagram of the disk drive
of FIG. 1.
[0011] FIG. 4 sets forth a flowchart of method steps for power
management in a data storage device that includes a magnetic
storage device, according to one or more embodiments.
[0012] For clarity, identical reference numbers have been used,
where applicable, to designate identical elements that are common
between figures. It is contemplated that features of one embodiment
may be incorporated in other embodiments without further
recitation.
DETAILED DESCRIPTION
[0013] FIG. 1 is a schematic view of an exemplary disk drive,
according to one embodiment. For clarity, disk drive 100 is
illustrated without a top cover. Disk drive 100 includes at least
one storage disk 110 that is rotated by a spindle motor 114 and
includes a plurality of concentric data storage tracks. Spindle
motor 114 is mounted on a base plate 116. An actuator arm assembly
120 is also mounted on base plate 116, and has a slider 121 mounted
on a flexure arm 122 with a read/write head 127 that reads data
from and writes data to the data storage tracks. Flexure arm 122 is
attached to an actuator arm 124 that rotates about a bearing
assembly 126. Voice coil motor 128 moves slider 121 relative to
storage disk 110, thereby positioning read/write head 127 over the
desired concentric data storage track disposed on the surface 112
of storage disk 110. Spindle motor 114, read/write head 127, and
voice coil motor 128 are coupled to electronic circuits 130, which
are mounted on a printed circuit board 132. Electronic circuits 130
include a read/write channel 137, a microprocessor-based controller
133, random-access memory (RAM) 134 (which may be a dynamic RAM and
is used as a data buffer), and/or a flash memory device 135 and
flash manager device 136. In some embodiments, read/write channel
137 and microprocessor-based controller 133 are included in a
single chip, such as a system-on-chip 131. In some embodiments,
disk drive 100 may further include a motor-driver chip 125, which
accepts commands from microprocessor-based controller 133 and
drives both spindle motor 114 and voice coil motor 128.
[0014] For clarity, disk drive 100 is illustrated with a single
storage disk 110 and a single actuator arm assembly 120. Disk drive
100 may also include multiple storage disks and multiple actuator
arm assemblies. In addition, each side of storage disk 110 may have
an associated read/write head coupled to a flexure arm.
[0015] When data are transferred to or from storage disk 110,
actuator arm assembly 120 sweeps an arc between an inner diameter
(ID) and an outer diameter (OD) of storage disk 110. Actuator arm
assembly 120 accelerates in one angular direction when current is
passed in one direction through the voice coil of voice coil motor
128 and accelerates in an opposite direction when the current is
reversed, thereby allowing control of the position of actuator arm
assembly 120 and attached read/write head 127 with respect to
storage disk 110. Voice coil motor 128 is coupled with a servo
system known in the art that uses the positioning data read from
servo wedges on storage disk 110 by read/write head 127 to
determine the position of read/write head 127 over a specific data
storage track. The servo system determines an appropriate current
to drive through the voice coil of voice coil motor 128, and drives
said current using a current driver and associated circuitry.
[0016] Disk drive 100 may be configured as a disk drive, in which
non-volatile data storage is generally only performed using storage
disk 110 in typical operation. Alternatively, disk drive 100 may be
configured as a hybrid drive, in which non-volatile data storage
can be performed using storage disk 110 and/or flash memory device
135. In a hybrid drive, non-volatile memory, such as flash memory
device 135, supplements the spinning storage disk 110 to provide
faster boot, hibernate, resume and other data read-write
operations, as well as lower power consumption. Such a hybrid drive
configuration is particularly advantageous for battery operated
computer systems, such as mobile computers or other mobile
computing devices. In a preferred embodiment, flash memory device
135 is a non-volatile solid state storage medium, such as a NAND
flash chip that can be electrically erased and reprogrammed, and is
sized to supplement storage disk 110 in disk drive 100 as a
non-volatile storage medium. For example, in some embodiments,
flash memory device 135 has data storage capacity that is orders of
magnitude larger than RAM 134, e.g., gigabytes (GB) vs. megabytes
(MB).
[0017] FIG. 2 illustrates an operational diagram of disk drive 100
with elements of electronic circuits 130 shown configured according
to one embodiment. As shown, disk drive 100 includes RAM 134, flash
memory device 135, a flash manager device 136, system-on-chip 131,
and a high-speed data path 138. Disk drive 100 is connected to a
host 10, such as a host computer, via a host interface 20, such as
a serial advanced technology attachment (SATA) bus.
[0018] In the embodiment illustrated in FIG. 2, flash manager
device 136 controls interfacing of flash memory device 135 with
high-speed data path 138 and is connected to flash memory device
135 via a NAND interface bus 139. System-on-chip 131 includes
microprocessor-based controller 133 and other hardware (including
read/write channel 137) for controlling operation of disk drive
100, and is connected to RAM 134 and flash manager device 136 via
high-speed data path 138. Microprocessor-based controller 133 is a
control unit that may include a microcontroller such as an ARM
microprocessor, a hybrid drive controller, and any control
circuitry within disk drive 100. High-speed data path 138 is a
high-speed bus known in the art, such as a double data rate (DDR)
bus, a DDR2 bus, a DDR3 bus, or the like.
[0019] In general, data storage devices with rotatable storage
disks, such as disk drives, can be configured to minimize energy
use by changing to lower power-consumption states when the data
storage device is not being used to satisfy read or write commands
from a host device. This is particularly true for disk drives used
in battery-powered devices, such as laptop computers. For example,
when a data storage device has not received host commands for a
predetermined time period, the data storage device may change from
an active servo state to an intermediate power consumption state, a
park state, or a standby state. In contrast, according to various
embodiments, a data storage device changes from a first power
consumption state to a second power consumption state based on a
time interval in which a rotatable storage disk or disks of the
data storage device are not accessed to satisfy read or write
commands. For example, in reference to disk drive 100 illustrated
in FIGS. 1 and 2, when read or write commands are exclusively
satisfied using RAM 134 and/or flash memory device 135, actuator
arm assembly 120, voice coil motor 128, spindle motor 114,
read/write channel 137 and/or microprocessor-based controller 133
may be operated at a lower power consumption state, since storage
disk 110 is not being accessed.
[0020] FIG. 3 illustrates a power-state diagram 300 for disk drive
100 that includes multiple power states and power state transitions
of disk drive 100. Power states in power-state diagram 300 include
an active servo state 310, an intermediate power consumption state
320, a park state 330, a standby state 340, and a sleep state 350.
State transitions in power-state diagram 300 include a float timer
expiration 311, a standby transition 312, a sleep command 313, a
park timer expiration 321, and an active servo transition 341.
While the elements of power-state diagram 300 are described in
terms of disk drive 100, it should be recognized that power-state
diagram 300 is applicable to any suitable data storage device that
includes a rotatable storage disk.
[0021] Active servo state 310 represents normal operation of disk
drive 100 to facilitate the execution of read and write commands,
either from host 10 or initiated by disk drive 110 itself. In
active servo state 310, the servo system of disk drive 100 actively
controls the position of read/write head 127 with respect to
individual tracks on storage disk 110, using voice coil motor 128,
actuator arm 124, and read/write channel 137. It is noted that disk
drive 100 may be in active servo state 310 when read or write
commands are not being serviced by disk drive 100. However, because
significant electrical energy is used by microprocessor-based
controller 133 and read/write channel 137 in active servo state
310, in some embodiments, disk drive 100 changes to a lower power
consumption state when one or more conditions are met. As shown in
FIG. 3, these conditions may include one or more of: float timer
expiration 311, standby transition 312, and sleep command 313.
[0022] When float timer expiration 311 occurs, disk drive 100
changes from active servo state 310 to intermediate power
consumption state 320, which is described below. Float timer
expiration 311 can be configured to take effect when no commands
are satisfied by accessing storage disk 110 for more than a
predetermined period of time. For example, a typical duration for
such a predetermined time period may be approximately 50 to 150
milliseconds. In some embodiments, a float timer is started when a
command, i.e., a read or write command, is satisfied by accessing
storage disk 110. The float timer is reset to zero and restarted
when a received command is satisfied by accessing storage disk 110.
Thus, float timer expiration 311 takes effect when the float timer
exceeds the predetermined time period described above, and disk
drive 100 changes to intermediate power consumption state 320. In
some embodiments, any read or write commands satisfied by accessing
storage disk 110 resets the float timer to zero, and in other
embodiments, only read or write commands that are both satisfied by
accessing storage disk 110 and that are received from host 10 reset
the float timer to zero.
[0023] It is noted that commands (either received by disk drive 100
from host 10 or initiated by disk drive 100 itself) that are
satisfied without accessing storage disk 110 do not reset the
above-described float timer. Consequently, even though read and/or
write commands are frequently received by disk drive 100 from host
10 and/or initiated by disk drive 100, portions of disk drive 100
associated with storage disk 110 can be changed from active servo
state 310 to intermediate power consumption state 320 when said
commands are satisfied by accessing RAM 134 and/or flash memory
device 135 but not storage disk 110.
[0024] When standby transition 312 occurs, disk drive 100 changes
from a current energy consumption state to standby state 340, in
which disk drive 100 spins down storage disk 110, read/write head
127 is parked, and disk drive 100 expends essentially no energy on
mechanical operations. Standby transition 312 may occur when disk
drive 100 is in one of several power states, including active servo
state 310, intermediate power consumption state 320, and park state
330. In some embodiments, standby transition 312 can be configured
to take effect when either one of two conditions are met: 1) no
commands from host 10 are satisfied by accessing storage disk 110
for more than a predetermined period of time, and 2) when a
"standby" command is received from host 10. In other embodiments,
standby transition 312 can be configured to take effect when: 1) no
commands from host 10 or initiated by disk drive 100 are satisfied
by accessing storage disk 110 for more than a predetermined period
of time, and 2) when a "standby" command is received from host
10.
[0025] Generally, the predetermined period of time associated with
standby transition 312 is substantially longer than that associated
with float timer expiration 311. For example, a typical duration of
time associated with initiating standby transition 312 can be on
the order of several minutes rather than milliseconds. In some
embodiments, a standby timer is started when a command is satisfied
by accessing storage disk 110, and the standby timer is reset to
zero and restarted when a command is next satisfied by accessing
storage disk 110. In other embodiments, the standby timer is
started when a command received from host 10 is satisfied by
accessing storage disk 110, while a command that is initiated by
disk drive 110 and is satisfied by accessing storage disk 110 does
not reset the standby timer to zero.
[0026] When standby transition 312 occurs, i.e., when the standby
timer exceeds the predetermined time period described above, disk
drive 100 changes to standby state 340. In some embodiments,
commands that are 1) received by disk drive 100 from host 10 or
initiated by disk drive 100 itself, and 2) are satisfied without
accessing storage disk 110, do not generally reset the
herein-described standby timer.
[0027] Sleep command 313, when received from host 10, causes disk
drive 100 to change from a current power state to sleep state 340.
Sleep command 313 may occur when disk drive 100 is in one of
several power states, including active servo state 310,
intermediate power consumption state 320, and park state 330.
[0028] Intermediate power consumption state 320, in which the servo
system of disk drive 100 is not used to provide continuous position
control of read/write head 127, uses less power than active servo
state 310 and more power than park state 330. For example, in some
embodiments, microprocessor-based controller 133 may apply a
predetermined constant bias to voice coil motor 128 to hold
read/write head 127 in place, thereby "floating" read/write head
127 rather than actively servoing the position of read/write head
127. In alternative embodiments, a low-frequency servo mode may be
used in intermediate power consumption state 320, in which limited
servo control is used to position read/write head 127 in an
approximate location. For example, the servo system of disk drive
100 may be activated for a single or a relatively small number of
samples for each revolution of storage disk 110, so that the
position of read/write head 127 is approximately known without the
relatively high energy cost associated with constantly servoing
read/write head 127 over a particular data storage track of storage
disk 110.
[0029] While using less energy than active servo state 310,
intermediate power consumption state 320 allows relatively fast
response to read or write commands that involve accessing storage
disk 110. For example, when disk drive 100 is in intermediate power
consumption state 320 and receives a read or write command, seeking
to a desired location on storage disk 110 in response to said
command can be completed in a few milliseconds to a few tens of
milliseconds. In contrast, when disk drive is in park state 320,
seeking to a desired location on storage disk 110 in response to
said command generally requires a few hundred milliseconds. In some
embodiments, disk drive 100 changes from intermediate power
consumption state 320 to a lower power consumption state when one
or more conditions are met. As shown in FIG. 3, these conditions
may include one or more of: standby transition 312, sleep command
313 (both described above) and park timer expiration 321.
[0030] When park timer expiration 321 occurs, disk drive 100
changes from intermediate power consumption state 320 to park state
330. In park state 330, storage disk 110 continues to spin at the
normal rotational velocity, but read/write head 127 is parked to
reduce aerodynamic resistance to spinning the data storage disk. In
this way, current required for the rotation of storage disk 110 is
reduced. Furthermore, in park state 330, read/write head 127 is
protected from mechanical shock experienced by disk drive 100. Park
timer expiration 321 can be configured to take effect when no
commands are satisfied by accessing storage disk 110 for more than
a predetermined period of time. Alternatively, park timer
expiration 321 can be configured to take effect when no commands
from host 10 are satisfied by accessing storage disk 110 for more
than a predetermined period of time.
[0031] Generally, the predetermined period of time associated with
park timer expiration 321 is substantially longer than that
associated with float timer expiration 311. For example, a typical
duration of time associated with park timer expiration 321 can be
on the order of several minutes rather than the milliseconds
associated with float timer expiration 311. In some embodiments, a
park timer is started when a command is satisfied by accessing
storage disk 110, and the park timer is reset to zero and restarted
when a command is satisfied by accessing storage disk 110. When
park timer expiration 321 occurs, i.e., when the park timer exceeds
the predetermined time period described above, disk drive 100
changes to park state 330. It is noted that commands that are
satisfied without accessing storage disk 110 do not generally reset
the herein-described park timer. Said commands can be either
received by disk drive 100 from host 10 or initiated by disk drive
100 itself, such as when controller 133 determines that data stored
in flash memory device 135 should be written on data storage disk
110.
[0032] In addition to changing to a lower power consumption state
when certain events occur, e.g., float timer expiration 311,
standby transition 312, sleep command 313, and park timer
expiration 321, disk drive 100 may also change to a higher power
consumption state when certain events occur. Specifically, when
active servo transition 341 occurs, disk drive 100 may be
configured to change to active servo state 310, as shown in FIG. 3.
In some embodiments, active servo transition 341 takes place when a
read or write command is satisfied by accessing storage disk 110.
For example, if a current version of the data associated with a
read command from host 10 is not stored in RAM 134 or flash memory
135, storage disk 110 is accessed by microprocessor-based
controller 133 to satisfy said read command. Thus, even when disk
drive 100 is in a low power consumption state, such as standby
state 340 or park state 330, disk drive 100 changes to active servo
state 310 so that storage disk 110 can be accessed to satisfy the
command received from host 10.
[0033] In some embodiments, disk drive 100 may change to active
servo state 310 in response to data being flushed to storage disk
110 from flash memory device 135. For example, when disk drive 100
is configured as a hybrid drive, a portion of flash memory device
135 may be used to store "dirty" data, which are data that are only
stored in flash memory device 135 and are not also stored on
storage disk 110. Furthermore, disk drive 100 may also be
configured to maintain a predetermined maximum threshold for the
portion of flash memory device 135 used to store dirty data. When
said maximum threshold is exceeded, disk drive 100 generally
"flushes" excess dirty data to storage disk 110, i.e., disk drive
100 writes a corresponding copy of the excess dirty data on storage
disk 110, and flags the copied data in flash memory device 135 as
"non-dirty" data. Thus, in some situations, disk drive 100 may
flush dirty data to storage disk 110, even though disk drive 100 is
in intermediate power consumption state 320, park state 330, or
standby state 340. In such situations, disk drive 100 changes to
active servo state 310 so that the data flushing process can be
performed. For example, after disk drive 100 changes to a lower
power consumption state as a result of float timer expiration 311,
standby transition 312, sleep command 313, or park timer expiration
321, host 10 may then send write commands to disk drive 100.
Ordinarily, disk drive 100 may accept write data directly into
flash memory device 135 to prevent activating the portions of disk
drive 100 associated with storage disk 110. However, if flash
memory device 135 is full or already stores the maximum allowable
quantity of dirty data, microprocessor-based controller 133 will
change the power state of disk drive 100 to active servo state 310
and begin to copy dirty data in flash memory device 135 to storage
disk 110.
[0034] In some embodiments, storage disk 110 may be accessed as a
result of other activities besides in response to commands from
host 10. Advantageously, in such embodiments, timers for measuring
time elapsed since storage disk 110 was last accessed in response
to a host command may not be affected when storage disk 110 is
accessed as a result of said non-host related activities. For
example, dirty data being flushed from flash memory device 135 or
RAM 134 may be considered such non-host related activities.
[0035] FIG. 4 sets forth a flowchart of method steps for power
management in a data storage device that includes a magnetic
storage device, according to one or more embodiments. Although the
method steps are described in conjunction with disk drive 100 in
FIGS. 1 and 2, persons skilled in the art will understand that
method 400 may be performed with other types of data storage
systems. The control algorithms for method 400 may reside in and/or
be performed by microprocessor-based controller 133, host 10, or
any other suitable control circuit or system. For clarity, method
400 is described in terms of microprocessor-based controller 133
performing steps 410-450.
[0036] As shown, method 400 begins at step 410, where
microprocessor-based controller 133 or other suitable control
circuit or system receives a command that requires access to
storage disk 110. For example, the command received in step 410 may
be a read command when the only up-to-date version of data
associated with the read command is stored on storage disk 110. In
another example, the command received in step 410 may be a write
command, where insufficient storage space is available in flash
memory device 135 and/or RAM 134 for storing the data associated
with the write command. In yet another example, the command
received in step 410 may be a flush-cache command from host 10
requesting that disk drive 100 flush some or all dirty data in
flash memory device 135 and/or RAM 134 to storage disk 110. In yet
another example, the command received in step 410 may be a write
command initiated by disk drive 100 itself, such as when flash
memory device 135 stores equal to or greater than a maximum desired
quantity of dirty data.
[0037] In step 420, microprocessor-based controller 133 controls
access to storage disk 110 in response to the command received in
step 410. In step 420, data are written to and/or read from storage
disk 110 to satisfy the command received in step 410.
[0038] In step 430, microprocessor-based controller 133 starts a
timer function or other technically feasible time measurement
technique in response to storage disk 110 being accessed in step
420. Generally, the timer function is started upon completion of
access to storage device 110 in step 420, but in some embodiments
may be started in conjunction with said access.
[0039] In step 440, microprocessor-based controller 133 checks the
time interval measured by the timer function started in step 430.
In some embodiments, step 440 is performed periodically, for
example every 10 milliseconds. When the time interval measured by
said timer function exceeds a predetermined value, i.e., a desired
time interval has elapsed, method 400 proceeds to step 441. When
the time interval measured by said timer function does not exceed
the predetermined value, i.e., the desired time interval has not
yet elapsed, method 400 proceeds to step 450.
[0040] According to various embodiments, the time interval in
question is associated with one of the power state transitions to a
lower power consumption state, as described above in conjunction
with FIG. 3. Specifically, in some embodiments, the time interval
referenced in step 440 is the time associated with float timer
expiration 311, and may therefore be on the order of 10s to 100s of
milliseconds in duration. In other embodiments, the time interval
referenced in step 440 is the time associated with standby
transition 312, and may therefore be on the order of a few minutes,
to 10s of minutes in duration, and in some instances may be defined
by host 10. In yet other embodiments, the time interval referenced
in step 440 is the time associated with park timer expiration 321,
and may therefore be on the order of a few minutes or longer in
duration.
[0041] In step 441, microprocessor-based controller 133 changes the
power state of disk drive 100 from the current power state, e.g.,
active servo state 310, to a desired lower power consumption state,
such as intermediate power consumption state 320, park state 330,
or standby state 340. In some embodiments, in step 441 additional
power management processes described herein may be initiated, such
as checking for a condition causing disk drive 110 to change to an
even lower energy consumption state, such as standby state 340. In
such embodiments, the condition may be an elapsed time since
storage disk 110 has been accessed in order to satisfy a command.
For clarity, blocks illustrating such an additional power
management process are omitted from FIG. 4.
[0042] In some embodiments, during the course of method 400 disk
drive 100 may be changed to standby state 340 in response to a
standby command from host 10. In such embodiments, when a standby
command is received by microprocessor-based controller 133 from
host 10, microprocessor-based controller 133 terminates method 400
and immediately changes disk drive 10 to standby state 340.
[0043] In step 450, microprocessor-based controller 133 determines
whether access to storage disk 110 has been requested in order to
satisfy a command received since step 420. If such a request has
been received by microprocessor-based controller 133, method 400
proceeds back to step 420, where said command is satisfied by
accessing storage disk 110. If such a request has not been received
by microprocessor-based controller 133 since step 420, method 400
proceeds back to step 440, as shown in FIG. 4.
[0044] It is noted that in step 450, one or more commands may be
received by disk drive 100 since step 420 without resetting the
timer function started in step 430, as long as storage disk 110 is
not accessed in response to said host commands. For example, read
or write commands from host 10 that are satisfied using RAM 134
and/or flash memory device 135 do not reset the timer function in
step 401. Similarly, in some embodiments, flushing of dirty data
from flash memory device 135 to storage disk 110, when performed
internally as a non-host related activity by disk drive 100, does
not reset said timer function. In other embodiments, flushing of
dirty data from flash memory device 135 to storage disk 110, when
performed internally as a non-host related activity by disk drive
100, resets the some timer functions (e.g., a float timer for float
timer expiration 311 or a park timer for park timer expiration
321), but not for others (e.g., a standby timer for standby
transition 312). Furthermore, it is noted that method 400 may be
used to change disk drive 100 to any of the power states associated
with disk drive 100 that are lower in power consumption than active
servo state 310, including intermediate power consumption state
320, park state 330, and standby state 340.
[0045] While various embodiments described herein are in terms of a
hard disk drive, embodiments also include data storage devices that
include a data storage disk, such as an optical disk drive,
etc.
[0046] In sum, embodiments described herein provide systems and
methods for power management in a data storage device. The data
storage device selects one or more power states of the magnetic
storage device based on a time interval during which the magnetic
storage device is not accessed in response to a host command.
Consequently, the magnetic storage device can be advantageously
changed to a lower power consumption state even though the data
storage device is actively serving a host device.
[0047] While the foregoing is directed to specific embodiments,
other and further embodiments may be devised without departing from
the basic scope thereof, and the scope thereof is determined by the
claims that follow.
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