Finally, good SCSI drivers map bad blocks dynamically so that any bad block encountered during normal use is removed. If the disk does contain bad blocks, the disk cannot be used. This disk may be used if these bad blocks are mapped out. Back to top The Algorithm Disks that are error-free are initialized exactly as before. Sparing proceeds by making a second pass over the disk, writing and then reading back a test pattern.
Testing is done a single track at a time, as a compromise between speed and wasted space.
If there are any errors or retries during a test, the sectors are deemed bad. Otherwise, the blank HFS volume structure is written to the disk. Removes the bad spots from the volume bitmap of available free storage. The Finder does physical copies only on 1594 block disks as an optimized method of disk copying. In practice, this means that the first 50 sectors and the second to the last sector of a 1440K FDHD disk must be good.