Seek acoustics reduction with minimized performance degradation

Details Seek acoustics reduction with minimized performance degradation Seek acoustics reduction with minimized performance degradation

1999-12-30

2001-10-30

Hudspeth, David (Department: 2753)

Dynamic magnetic information storage or retrieval

Automatic control of a recorder mechanism

Controlling the head

C360S078090, C711S113000, C711S133000, C711S137000

Reexamination Certificate

active

06310743

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to disc drive data storage systems. More particularly, the present invention relates to methods and apparatus for performing a seek in a disc drive data storage system.
BACKGROUND OF THE INVENTION
A disc drive data storage system includes a data storage disc providing a disc surface that has concentric data tracks, a data head that can read/write to the disc surface, and an actuator which supports the data head above the disc surface. Movement of the actuator causes movement of the data head.
In disc drives, an access can be defined as the movement of the data head relative to the disc surface from the end of one read/write on the disc surface to the beginning of the next read/write on the disc surface, but not including the actual reading/writing. The access time is made up of two time components: seek time and latency time. The seek time component is the time taken to travel from the track on which one read/write completes to the track on which the next read/write begins. The second time component, the rotational latency time, includes the time the disc drive spends waiting for the appropriate data to rotate under the head after the head has arrived at the track on which the next read/write begins. The rotational latency time also includes the time the disc drive spends at a track after data has been read or written to the desired location. The rotational latency time can be a significant part of the access time for all but the longest seeks. It is the dominant component of the access time for relatively short seeks. In some disc drive data storage systems, commands sent by a host computer are executed in an optimum order to minimize both radial movement of the data head and also rotational latency.
In spite of the advantages gained by optimizing the execution of commands, lack of control over the number and size of commands and the time between commands arriving from the host computer imposes limitations in the optimization techniques. Thus, significant rotational latency still exists in current systems.
Access operations are typically a combination of rapid movement of the actuator that moves the data head to the desired track followed by a wait period for the appropriate data to come under the head. Rapid movement of the actuator causes problems in the disc drive data storage systems such as increased vibration, an increase of emitted acoustics, high power consumption, and generally a higher stress factor to the overall mechanics.
When performing read seeks, pre-fetch or post-fetch data can be obtained from the target data track during the latency period before the desired data rotates beneath the head and after the desired data is read. Accessing the pre-fetch and post-fetch data improves the drive performance, but results in increased acoustic noise due to the relatively high velocity of the seek required to arrive at the target track soon enough to read the pre-fetch data. Conventional just-in-time seeking, in contrast, calls for seek operations to be performed at the slowest possible velocity which allows the head to arrive at the data to be read by the time that location rotates beneath the head. This reduces the level of acoustic noise, but ignores the potential efficiency gains attainable by reading pre-fetch or post-fetch data in the same fetch operation as that of the target data.
The present invention provides a solution to this and other problems and offers other advantages over the prior art.
SUMMARY OF THE INVENTION
The present invention relates to disc drive data storage systems which reduce vibrations, acoustic noise and/or power consumption while minimizing performance degradation.
One embodiment of the present invention is directed to a method of controlling an actuator in a disc drive to perform a seek operation prior to a read operation. An indicator of the performance benefit to be gained by reading pre-fetch or post-fetch data is determined. Then a seek velocity profile is selected based on the indicator of the performance benefit that would be gained by reading pre-fetch and post-fetch data. The actuator then is controlled using the selected seek profile.
In one embodiment, prior to selecting a seek profile, the radial distance between the initial track and the target track is determined. A rotational distance between the initial head rotational position and the target rotational position is also determined. Then a seek velocity profile is selected based on the indicator of the performance benefit, the radial distance and the rotational distance.
In one embodiment, the indicator of the performance benefit that would be gained by reading pre-fetch and post-fetch data is derived in part from the radial seek length.
Another embodiment of the invention is directed to a disc drive data storage system having a data storage disc, a data head, an actuator and a controller. The data storage disc provides a disc surface. The data head is capable of reading data from the disc surface. The actuator supports the data head above the disc surface so that movement of the actuator causes movement of the data head. The controller controls the actuator to move the data head to a target location to implement a read operation in response to a request from a host. The controller is capable of generating an indicator of the magnitude of the performance benefit that would be gained by reading post-fetch data on the initial track prior to commencing the seek and by reading pre-fetch data on the target track after the seek and prior to reading the requested data. The controller is also capable of selecting a seek velocity profile for a read seek operation based on seek length and the indicator of the magnitude of the performance benefit that would be gained by reading pre-fetch or post-etch data.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.


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“Optimizing Inactive Optical Drive Activity,” IBM TDB vol. 37, pp. 435-438, Jun. 1994.

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