Adaptive update of seek time prediction data

Details Adaptive update of seek time prediction data Adaptive update of seek time prediction data

1999-03-29

2003-02-04

Sniezek, Andrew L. (Department: 2651)

Dynamic magnetic information storage or retrieval

Automatic control of a recorder mechanism

Controlling the head

C360S078080, C360S078140

Reexamination Certificate

active

06515819

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to methods and apparatus for use in disk drives for computer systems. More particularly, the present invention relates to methods and apparatus for adaptively updating seek time prediction data.
2. Description of the Related Art
The reduction of the time required to access data in disk drives is crucial to ensure that performance issues associated with a disk drive may be minimized. When performance of a disk drive is not at an acceptable level, customer dissatisfaction regarding the disk drive may be significant, and the time required to access data stored on the disk drive may be compromised. By way of example, when a disk drive experiences a time delay during access of data stored on the disk drive, a customer may perceive the disk drive to be operating in a faulty manner. Therefore, the magnitude of time delays experienced on a disk drive during access of data stored on the disk drive must generally be reduced to acceptable levels.
FIG. 1
is a diagrammatic representation of a disk drive assembly suitable for use in a computer system. A disk drive assembly
102
, which may also be known as a head-disk assembly (HDA), includes a platter assembly
104
that is situated on a base plate
103
. Platter assembly, as shown, includes a platter
105
and a spindle mechanism
106
. Spindle mechanism
106
typically includes a spindle bearing
107
which is coupled to platter
105
, or a disk. Data is stored, or otherwise encoded, on the disk
105
. The data may be stored on the disk
105
in multiple tracks
108
, each of which includes encoded position information. That is, each track
108
contains track numbers and patterns to determine fractional positions which relate to the location of a disk drive, or read/write, head
120
with respect to the disk
105
.
Disk drive assembly
102
also includes an actuator assembly
114
. Actuator assembly
114
includes an actuator
118
which supports disk drive head
120
. Actuator assembly
114
is arranged to move disk drive head
120
to different positions over the disk
105
such that data may be retrieved from or stored to different data-carrying sectors of the disk
105
. In general, when disk drive head
120
is to be moved, torque is generated to pivot or otherwise move actuator assembly
114
by a motor assembly
122
. Motor assembly
122
is generally mechanically coupled to actuator assembly
114
through an actuator bearing
124
.
Actuator motor assembly
122
often includes a coil structure and a magnetic field which surrounds the coil structure, as will be appreciated by those skilled in the art. In other words, actuator motor assembly
122
typically includes a voice coil motor (VCM). By passing current through the coil structure in a particular direction and for a specified length of time, actuator assembly
114
may be moved, e.g., pivoted, such that disk drive head
120
is positioned over a specific portion of the disk
105
. The pivoting of actuator assembly
114
to position the disk drive head
120
in a desired position is generally known as a “seek.” The time to perform each seek is typically known as “seek time.” A spindle bearing
107
, which is coupled to a spindle motor (not shown), allows the disk
105
to rotate with respect to base plate
103
. The time required to rotate the disk
105
to perform a particular data access may be termed “rotation time.” The rotation time is equal to the time required to rotate from a current position to a desired position on the disk
105
. Thus, the rotation time may be as great as the time required for one revolution of the disk
105
. Generally, the total time to access a particular block of data stored on the disk is approximately equal to the sum of the seek time, the rotation time, and the time required to read or write the data.
When multiple seek commands are received, the order in which the commands are processed may be determined by the total time required to access each of the corresponding data blocks. As shown, the disk may rotate in a direction indicated by arrow
126
. In addition, a first data block
128
, a second data block
130
, and a third data block
132
are illustrated. As shown in
FIG. 1
, the first data block
128
has rotated past the disk drive head
120
. Thus, if the first data block
128
is accessed first, a delay approximately equal to the rotation time is imposed. As a result, it is typically preferable to read the data block that is closest to the disk drive head
120
and which has not rotated past the disk drive head
120
. By way of example, it may be preferable to access the second data block
130
since it is closest to the disk drive head
120
in the rotation path of the disk
105
. Thus, the total time required to access each data block stored on the disk
105
is dependent upon the location of the data being accessed.
As described above, the order in which the seek commands are selected and executed is preferably determined, at least in part, by the total time required to access each data block. The rotation time is dependent upon the revolutions per minute (RPM) of the disk
105
and may therefore be easily calculated. However, the seek time is dependent upon the distance between the data being accessed and the disk drive head
120
. Therefore, it would be beneficial if these seek times could be accurately predicted.
Expected seek times associated with various seek commands may be tracked through the use of a seek time table. As shown in
FIG. 2
, an exemplary, conventional seek time table is shown. The seek time table includes a plurality of entries
202
. Each one of the plurality of entries
202
includes a distance
204
and a seek time
206
that may be required to access data located at the distance from the disk drive head. Typically such a table is static and maintained for multiple disk drives rather than one disk drive. However, disk drives often have varying operating characteristics (e.g., seek times). Moreover, each individual disk drive may operate in a different manner depending upon the operating environment (e.g., temperature, voltage) of the disk drive. As a result, the seek time table may be inaccurate under a variety of circumstances. Accordingly, the total time required to access each data block may be greater than desired.
Inaccuracies associated with the seek time table may have a negative effect on the total time required to access one or more data blocks. By way of example, the seek time table may be presented in the form of a “seek time curve” such as that illustrated in FIG.
3
. Seek times
302
are plotted along the y-axis while distances
304
associated with the seek times are plotted along the x-axis. As shown in
FIG. 3
, the slope of “seek time curve”
306
is highest when the disk drive head must traverse short distances. Since misprediction of seek times may result in rotation of a selected data block past the disk drive head
120
, this may result in an unnecessary delay equal to the rotation time as the data block again rotates toward the disk drive head
120
. As a result, the cost of error is high, particularly for these short distances. Accordingly, it would be beneficial if seek times could be accurately predicted for various distances, disk drives, and operating environments.
SUMMARY OF THE INVENTION
The invention relates to methods and apparatus for adaptively updating a set of seek time data for use in a disk drive apparatus. In accordance with one embodiment of the invention, the disk drive apparatus includes a disk drive head and the set of seek time data includes a plurality of data points. Each of the plurality of data points is defined-by a distance and an expected seek time during which the disk drive head may be traversed across the distance.
According to one aspect of the invention, methods and apparatus for processing a seek request on a disk drive apparatus having a disk drive head are provided. The seek request is processed during which the disk drive head is traversed across an act

Affiliated with

Also associated with

Rating

Adaptive update of seek time prediction data does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Adaptive update of seek time prediction data, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Adaptive update of seek time prediction data will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3131158