How does dual parity work, actually?


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10 hours ago, trurl said:

Unraid monitors these things for you but you should set up Notifications to alert you immediately by email or other agent so you will know without even opening the webUI.

Thank you, and yes, I have had notification setup for years :-)

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  • 1 year later...

I know it's an old topic but is there something that detects bitrot (of any type, including bad sectors), and fixes the lost data be rescuing it using the parity, on a regular basis on unRAID? I read there is something like this in synology so I'm hoping to not have to buy synology but instead self-build.

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1 hour ago, Bob2 said:

I know it's an old topic but is there something that detects bitrot (of any type, including bad sectors), and fixes the lost data be rescuing it using the parity, on a regular basis on unRAID? I read there is something like this in synology so I'm hoping to not have to buy synology but instead self-build.

When a drive fails a read request, all the rest of the drives are read, the failed read request is fulfilled from the resulting parity calculation, and that data is written back to the drive that failed the read request. If that write fails, then the drive is marked as invalid (red X) and the parity calculations are used for all further I/O to that drive slot, the physical drive is no longer accessed.

 

That is the total extent of what Unraid does by default, anything beyond that would need to be handled by recovery from backups.

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