Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1998-07-31
2001-06-26
Bragdon, Reginald G. (Department: 2186)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S111000, C710S005000
Reexamination Certificate
active
06253279
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of determining the data layout geometry of a disk drive by applying a novel access pattern and interpretation of the measured results.
BACKGROUND OF THE INVENTION
Modem disk drives store data in blocks with a fixed size. The physical block in a drive are termed sectors. The sectors are arranged in tracks, each track having a fixed number of sectors, and the tracks are arranged in cylinders. Many of today's magnetic disk drives employ zone recording, where all tracks within a zone have the same number of sectors per track. The sectors may be skewed from track to track and from cylinder to cylinder.
These disk drive parameters, namely, a number of tracks per cylinder, number of zones, number of sectors per track in each zone, track skew, and cylinder skew, define the data layout geometry of a disk drive. These parameters affect the performance characteristics of a disk drive. An additional parameter that affects the disk drive performance is the drive's rotational speed. A need arises for a technique with which these disk drive parameters may be quickly and easily determined, for any disk drive encountered.
SUMMARY OF THE INVENTION
The present invention is a system and method for determining the disk drive parameters of any disk drive that may be encountered. By applying a special access pattern to the disk drive and a special technique of interpreting the measured results, the present invention can determine the number of data tracks per cylinder, the number of recording zones, number of sectors per track in each zone, the track skew, the cylinder skew, and the rotational speed of the disk drive.
In order to determine a data layout geometry of a disk drive, a plurality of sectors on the disk drive are accessed in sequentially decreasing order, starting from an initial sector. A completion time for each access is measured and parameters related to the data layout geometry of the disk drive are determined based on the measured access times. In order to determine the layout geometry, sectors immediately preceding track and cylinder skews are identified and a number of sectors per track and a number of tracks per cylinder are determined based on the identified sectors.
In order to identify the sectors, an average completion time of all measured access times is determined. All measured access times that are less than the average completion time by at least a predefined threshold are identified. A standard completion time, which is an average of all measured access times, excluding those measured access times that are less than the average completion time by at least the predefined threshold, is determined. Logical block addresses corresponding to the measured access times that are less than the average completion time by at least the predefined threshold are identified. A skew time for each identified logical block address is determined by subtracting the measured access time for the logical block address from the standard reference time and each skew time is identified as either a track skew or a cylinder skew based on the size of the skew time.
A number of sectors per track is determined based on a sector distance between identified sectors immediately preceding track skews and a number of tracks per cylinder is determined based on a number of tracks between identified sectors immediately preceding cylinder skews. A rotational speed of the disk drive is determined based on the determined number of sectors per track and the determined standard reference time in accordance with:
rpm=60×(
S−l
)/(
S×T
),
where rpm is the rotational speed of the disk drive, S is the number of sectors per track and T is the standard reference time.
In another embodiment of the present invention, a zone layout of the disk drive is determined by repeatedly determining a number of sectors per track at a plurality of locations on the disk drive. Each determination is made using a different initial sector sector. The initial sector to be used for each determination is selected from the set {0, W/X, 2W/X, 3W/X, . . . , (X−1)W/X)}, wherein W is the maximum logical block address of the disk drive and X is a positive integer.
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IBM Technical Disclosure Bulletin, Adaptive Skew Optimization, Oct. 1995, pp. 559-562.*
Worthington et al., “On-Line Extraction of SCSI Disk Drive Parameters”, 1995, 146-156.*
Aboutabl et al., “Temporally Determinate Disk Access: An Experimental Approach”, 1998.
Bragdon Reginald G.
International Business Machines - Corporation
Morgan & Finnegan , LLP
Peugh Brian R.
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