On 823 we lost around 12% using data loss option, we could not go for backup since the they were configured directly to tapes which would have taken more time to restore for 600GB or more database and backup tool Legato customer used was not that reliable.

So we checked the table rows before and after , estmated aorund 29K rows lost and luckily data stored on the table was not critical.

Good reilable backup's need to be in place to recover form errors on clustered index table's, yes CRC errors some times mey be hardware related which can determined by SYSTEM's logs.