November 21, 20205 yr I'm trying to understand the sequences of events before and after a disk failure in UnRaid. Just trying to prepare myself. When UnRaid detects a single CRC error, does it just disable the drive? How do I know to replace the drive? Do I just rebuilt it and try again? Or, fire it into the garbage and replace? How do I know when to replace a drive? Do I just rely on the SMART results and my own intuition? I sort of assumed a disk's firmware kept track of good & bad sectors, and raid systems worked behind the scenes shuffling & re-writing files as required. I don't think that's the case? I think it's one CRC error, and the drive is disabled? Just trying to understand, so I know what to do. PS: If this discussion has been discussed before, please send me a link. I'm assuming it has.
November 21, 20205 yr Discussed many, many times. Here's one discussion on error recovery. Search this site for red ball, disk disabled, etc. https://forums.unraid.net/topic/58028-parity-check-finished-with-errors-not-sure-how-to-proceed/?do=findComment&comment=569114 Typically CRC errors aren't bad drives, more often they are bad cables. If you have notifications set up, Unraid will tell you when one of the monitored smart attributes changes.
November 22, 20205 yr Community Expert 13 hours ago, Greggy said: I think it's one CRC error, and the drive is disabled? Unraid will only disable a disk if a WRITE to it fails. As was mentioned CRC errors are connection related and are very rarely a genuine disk issue. They only cause a retires to occur and as long as a retry succeeds then things continue otherwise unaffected. One thing to be aware of with CRC errors is that there is no way to set the count back to 0 - it can only increase, so if it stops increasing after taking some rectification action that is all you can expect.
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