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Recovery From Defective Tape During Restore Operation

IP.com Disclosure Number: IPCOM000042232D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Koeller, PD: AUTHOR [+2]

Abstract

When restoring data from tapes that contain a physical copy of disk storage, a method is required to bypass defective blocks on the tape. Such a method would enable the remainder of the tape to be restored. The following definitions apply. "Sector" refers to the smallest physical partition which can be addressed on the disk, and "block" refers to the smallest physical partition which can be addressed on the tape. Note that one block which is written on tape will contain the data from multiple disk sectors. Tapes can be damaged so that the data on them cannot be read. Normally when the tape has been damaged, the restore procedure handles the situation in one of two ways: 1. The restore procedure terminates when the damaged tape is encountered. This method prevents the rest of the data on the tape from being restored. 2.

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Recovery From Defective Tape During Restore Operation

When restoring data from tapes that contain a physical copy of disk storage, a method is required to bypass defective blocks on the tape. Such a method would enable the remainder of the tape to be restored. The following definitions apply. "Sector" refers to the smallest physical partition which can be addressed on the disk, and "block" refers to the smallest physical partition which can be addressed on the tape. Note that one block which is written on tape will contain the data from multiple disk sectors. Tapes can be damaged so that the data on them cannot be read. Normally when the tape has been damaged, the restore procedure handles the situation in one of two ways: 1. The restore procedure terminates when the damaged tape is encountered. This method prevents the rest of the data on the tape from being restored. 2. The save procedure continues past the damaged tape. When this occurs, there is no way to determine what data has been lost. When a restore of the data from tape is required, the restore procedure will read the data from the tape and write it onto the disk at the same disk address from which the data was originally saved. This procedure requires that all of the data can be read from the tape at restore time. The save procedure has the following requirements: - The data must be saved in sequential disk address order. - Each block of data which is written to the tape must include the sector address of the first sector of data which is contained in the block. - Each block of data which is written to the...