TITLE
    Drive Setup: Test Disk Sector Sparing and Error Messages
Article ID:
Created:
Modified: 		24530
8/10/98
8/10/98
TOPIC

    During Test Disk, does Apple HD SC Setup/Drive Setup perform sector sparing?

    Drive Setup may report 1 of 4 messages after Test Disk is performed. Under what circumstances would someone receive each of the following errors in Drive Setup?

      1. This disk needs a low-level format.
      2. The test is complete. A few recovered errors occurred.
      3. The test was interrupted because too many errors occurred.
      4. The test was interrupted. An unrecoverable error occurred and could not be fixed.

DISCUSSION

    Question: During Test Disk, does Apple HD SC Setup/Drive Setup perform sector sparing?

    Sector sparing, often referred to as block reallocation, is explicity performed for SCSI drives during test disk. It may not be performed at other times. No explicit sparing is performed for ATA drives as block sparing is supposed to be automatically carried out by the drive's firmware.

    Question: Drive Setup may report 1 of 4 messages after Test Disk is performed. Under what circumstances would someone receive each of the following errors in Drive Setup?

    1. This disk needs a low-level format.
    Drive Setup will poll each drive to identify device characteristics. During this process, 10 blocks of the surface are each read and written back. If a "Media format is corrupted" error is reported by the drive via the extended sense code, the disk probably needs a low-level format. In the case of SCSI drives, this means that header information must be written to every sector on the disk. No such error should be reported for ATA drives. Note that MO devices may report an extended sense code indicating "Not formatted".

    2. The test is complete. A few recovered errors occurred.
    During the test process, internal counters are maintained for data integrity errors, most likely checksum errors, recovered errors, and non-recovered errors. Non recovered errors are considered serious enough to abort any further testing of the media. Drive Setup considers less than 10 recovered errors as fairly benign. The message "The test is complete. A few recovered errors occurred" means that less than 10 "soft" errors have been detected.

    3. The test was interrupted because too many errors occurred.
    4. The Test was interrupted. An unrecoverable error occurred and could not be fixed.
    The internal limits for non-recovered errors and data integrity errors are 0 and 0. The message "The test was interrupted because too many errors occurred" means that more than 0 non-recovered errors or 0 data integrity errors or 10 recovered errors have occurred.

    The priority in monitoring the error counters is:
      1. Non-recoverd errors take precedence over any other type of errors so these are check for first.
      2. Data integrity errors take precedence over soft errors.
      3. More than 10 soft errors.

Document Information
Product Area: Apple Software
Category: Utility Software
Sub Category: Hard Disk Setup Software

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