ReadyNAS 104, Firmware 6.10.10, Resync failure

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nhasenoehrl wrote:

 

I took out one of my 6TB Hard Disks for maintenance the other three worked fine, but of course the system said "data DEGRADED".

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Bad idea.  If you want to test a disk out of the NAS, you should always power down the NAS before removing the disk, and keep it powered down until the disk is reinserted. 

You can also test it in place, either using smartctl or the built-in disk test on the volume settings wheel (which also uses smartctl).  You can also schedule the NAS maintenance tasks on that settings wheel.

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nhasenoehrl wrote:

But when I put it back in it started Resync but failed somewhere at 30% or so. So I took it back out and formated it (on Win 11, via a docking station). Then I put it back in, now it started that whole lengthy resync process again. I hope it will work this time. Does the system expect an empty harddisk when it starts resync?

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Since the NAS was running, the disk you removed was out of sync with the NAS when you reinserted it.  So the NAS attempted to rebuild the contents of that disk from the parity blocks on the remaining disks - writing to every sector of the disk you reinserted. The system was NOT assuming the disk was empty.

If any of the remaining disks had failed during the resync process, you would have lost the entire volume.

You should download the full log zip, and look for disk errors during the resync that failed.  The most likely scenario is that this was a write failure to the drive you removed/reinserted.  FWIW, I've had disks that pass non-destructive read tests, but which fail a destructive write test (and vice versa).   But it's best not to guess.