Parity striping feature for optical disks

Details Parity striping feature for optical disks Parity striping feature for optical disks

1994-09-22

1995-05-02

Trammell, James P.

Excavating

371 101, 371 491, H03M 1300

Patent

active

054126681

ABSTRACT:
An apparatus and method for performing parity striping of optical disks for error recovery and data reconstruction. A parity group is created by identifying volumes and then setting a parity flag to indicate whether the data has been updated since a most recent writing of parity information. Parity striping is performed either partially or fully off-line or upon exporting the parity group from the storage array. The striping involves calculating parity, which may be done by Exclusive Or'ing the data and then writing parity to a parity disk. In one embodiment, the invention is implemented with any array of redundant optical disks. In another embodiment the invention is implemented with a redundant array of independent libraries. In either embodiment, striping may be performed when the media is archived to an external shelf. When the invention is implemented with a redundant array of independent libraries, striping may be performed in an intermittent fashion during background time. Intelligence is provided so that the striping method is employed with knowledge regarding the media format. In the case of magneto-optical media this means that the system is capable of recognizing pre-erased sectors. The system utilizes the format to reduce the work of striping and reconstruction. Because the system is programmed to recognize the pre-erased sectors, no error recovery is induced.

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