Re: Requesting assistance recovering RAID-5 array

Phil Turmel
2020-04-03T18:34:16Z

On 4/3/20 2:29 PM, Daniel Jones wrote:
> Hello again,
>
>> Don't do the --add operation until you've copied anything critical in the array to external backups (while running with 3 of 4).
>
> Everything from the array has been backed up elsewhere.
>
> Up until now the only writes intentionally done to the physical drives
> have been the new partition tables. Everything else has been through
> the overlay.
>
> Now I think I'm ready to run a --create as follows on the physical drives:
> mdadm --create /dev/md0 --assume-clean --data-offset=129536 --level=5
> --chunk=512K --raid-devices=4 missing /dev/sdc1 /dev/sdd1 /dev/sde1
>
> After that I'd try to re-add the rejected drive?
> mdadm --manage /dev/md0 --add /dev/sdb1
>
> Part of me wonders about just rebuilding the whole thing and then
> copying the data back, but I don't know that would be any better then
> this path.

Sounds like a risk-free decision. mdadm --create --assume-clean
followed by a proper fsck will be lots faster than mdadm --create, mkfs,
and copying.

I'd go fast.

Phil