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Method for Data Recovery for "Load/Unload on Data" in a Hard Drive Disclosure Number: IPCOM000013836D
Original Publication Date: 2000-Jun-01
Included in the Prior Art Database: 2003-Jun-18

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Loading and unloading magnetic recording heads on data is necessary in order to maximize capacity in hard drives. There are concerns, however, that a faulty load or unload operation(s) may destroy critical data such as servo marks, customer data, vital product tables, etc.. In order to eliminate this concern, this invention uses mirror images of data stored on the disk surfaces in areas where load/unload damage is likely to occur. To practice this invention requires some knowledge of the load/unload geometry. Specifically, the physical radii on the disk where head-disk contact may occur during head loading and unloading must be known in advance. In practice, this can be easily determined by the drive design, load ramp dimensions and tolerances, and airbearing geometry. Once the disk radii are known, these can be equated to logical block addresses (for example). A table of these LBAs for each disk surface is stored in non-volatile memory on the hard drive. When write commands are received by the drive, a table look-up will show if the data should be also written to a pre-defined mirrored site. The writing to a mirrored site can take place at any time, but preferably before the heads are unloaded. When data errors result in the load/unload areas of a disk, mirrored sites are used. A diagram that gives an overall view of the invention is shown in Fig. 1. At the disk outer diameter (OD), a likely load/unload damage zone has been identified by the cross-hatched area. Data from these areas on each disk surface is mirrored to the ID (in this case). The mirrored area is shown shaded. For performance reasons, data at the OD is preferable because of the higher data rate. It is therefore more likely that a drive may fill from OD to ID. This means that the mirrored sites will be the last physical areas to be used. 1