HDD Data Integrity and Performance Enhancement Via Redundant Recording in the Head Load/Unload Zone
Original Publication Date: 2001-Mar-01
Included in the Prior Art Database: 2003-Jun-18
Disclosed is a method allowing full usage of the load/unload zone and also serving as a secondary read cache with potential for improved seek and latency performance. Current Hard Disk Drives (HDDs) utilizing load/unload technology (e.g. ramp load/unload on mobile and IBM's recent server HDDs) do not record data in the zone at the outer diameter (OD) of the recording disks that lies underneath the area where the recording heads are unloaded. The zone is not used due to the concern that the heads may contact the disk during the load or unload operation, which could lead to permanent data loss from disk media damage or thermal erasure. Although the probability of head-disk contact during load/unload is fairly low with the present technology, it is finite and poses a tangible risk with respect to the integrity of customer data. The solution is to use redundant data recording within this zone (e.g. writing data twice, 180 degrees apart; or three times, 120 degrees apart, etc.) to insure that any data loss due to a localized head-disk incident can be recovered by simply reading the redundant copy of data on the same track. The advantages of this proposal include: 1) Efficient use of currently unusable prime recording real estate. The OD of the disk is the most efficient recording zone and the load/unload zone, which is typically larger than the slider width, could represent a loss of up to 5% of the potential recording area per disk. For a multidisk drive this loss is substantial. 2) Significant improvement in read performance. The latency during read operations is effectively reduced by a factor equal to the number of redundant recordings of the data.