DiskScan is a Unix/Linux tool to scan a block device and check
if there are unreadable sectors, in addition it uses read
latency times as an assessment for a near failure as sectors
that are problematic to read usually entail many retries. This
can be used to assess the state of the disk and maybe decide
on a replacement in advance to its imminent failure. The disk
self test may or may not pick up on such clues depending on
the disk vendor decision making logic.