Adding hard disks

Fixing bad tracks and bad blocks on hard disks

A bad track is an area of the hard disk that is not reliable for data storage. The hard disks supported by SCO OpenServer allow you to map the bad track into the bad track table that lists any areas of the hard disk that should not be used. The bad tracks listed on the table are aliased to good tracks so that the operating system avoids the areas of the disk that cannot be read or written.

If your hard disk develops a bad track after the system is installed and running, an error message like the following is displayed on the console:

   wd: ERROR on fixed disk ctlr=0 dev=0/47 block=31434 cmd=00000020
       status=00005180, sector = 62899, cylinder/head = 483/4

For a SCSI disk, the message is like this:

   NOTICE: Sdsk: Unrecoverable error reading SCSI disk 2 dev 1/64
              (ha=0 id=1 lun=0) block=219102
              Medium error: Unrecovered read error

If such an error occurs, use badtrk(ADM) to create a new bad track table so that the system can avoid the new bad track(s). The badtrk utility is a menu-driven utility for viewing, adding, or deleting entries in the bad track table. badtrk automatically enters any flaws it detects in the table, provided there is room. SCSI disks have a similar mechanism that maps bad SCSI logical blocks instead of bad tracks. By default, badtrk will try to add bad blocks to the drive's own internal defect list (G-list) if the drive supports this. You can use the -O option to badtrk to force badtrk to add the bad block to the table managed by the operating system. If your SCSI disk controller supports Automatic Read/Write Remapping (ARR/AWR), you can use badtrk to enable this feature. This allows recoverable errors to be automatically remapped whenever they occur.

To use badtrk, reboot the system and enter single-user mode. (Do not use shutdown su to do this.) Run badtrk, scan the disk, and the entire UNIX system partition. Choose either a quick or thorough scan; a thorough scan is recommended if new bad tracks have appeared. Select nondestructive mode to preserve the data on your hard disk. When the scan completes, quit, and return the system to multiuser mode.