ReadyNAS 716X data- Two volumes after Resync

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RN716x wrote:

Is it asking for an input here?

 

root@MaQBaLiNAS:~# cat /etc/mdadm/mdadm.conf

CREATE owner=root group=disk mode=0660 auto=yes

 

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This is the same as the file on my system, so nothing unusual here.

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RN716x wrote:

 

root@MaQBaLiNAS:~# mdadm --assemble --scan --force
mdadm: NOT forcing event count in /dev/sdc3(3) from 11031 up to 19055
mdadm: You can use --really-force to do that (DANGEROUS)
mdadm: /dev/md/data-0 assembled from 4 drives - not enough to start the array. 
mdadm: No arrays found in config file or automatically

 

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This is telling you that /dev/sdc3 is missing a lot of writes - so it is seriously behind the other drives in the array.

1. You could proceed with --really-force instead of force.  You could end up with a lot of data loss/corruption if you do that.
2. Another other option is go back to SDA.  Power down, remove SDC, insert the SDA. Power up, and try the same mdadm command again, and see if the event count gap is smaller. If you go this route, you should definitely mount the volume as read-only - as we know that SDA is failing, and writes will likely only accelerate that.  Also they would increase the event gap between sdc and the rest of the array (making going back to SDC even more risky).

This isn't an obvious decision.  SDA likely will have a smaller event gap, but we already know it has unreadable sectors.  Plus it might fail when you try to offload data. Still, I think it is likely the best path (with read-only mounting). 

A variant of (2) is to clone SDA, and insert the clone.  The cloning process will skip over any unreadable sectors on the original.  The benefit of the variant is that there will be no bad sectors detected on the clone (which is a mixed blessing, as bad sectors do give you some information on file corruption).  The risk is that the original will completely fail during the cloning process.

Either way (1, 2, or 2 variant), you'd copy off as much data as you can, do a factory default with the two new drives installed in place of SDA and SDC. You'd reconfigure the NAS at that point, and then restore the files from the backup.