Re: Raid 5 where 2 disks out of 4 were unplugged

Hello Gennaro,

Good report.

On 8/26/21 5:18 AM, Gennaro Oliva wrote:

Hello,
I have a QNAP with Linux 3.4.6 and mdadm 3.3. I have 4 drives assembled
in raid 5, two of those drives where accidentally removed and now they
are out of sync. This is a partial output of mdadm --examine

[trim /]

mdadm --verbose --assemble --force /dev/md1 /dev/sda3 /dev/sdb3 /dev/sdc3 /dev/sdd3
mdadm: looking for devices for /dev/md1
mdadm: failed to get exclusive lock on mapfile - continue anyway...
mdadm: /dev/sda3 is identified as a member of /dev/md1, slot 0.
mdadm: /dev/sdb3 is identified as a member of /dev/md1, slot 1.
mdadm: /dev/sdc3 is identified as a member of /dev/md1, slot 2.
mdadm: /dev/sdd3 is identified as a member of /dev/md1, slot 3.
mdadm: added /dev/sdb3 to /dev/md1 as 1
mdadm: added /dev/sdc3 to /dev/md1 as 2 (possibly out of date)
mdadm: added /dev/sdd3 to /dev/md1 as 3 (possibly out of date)
mdadm: added /dev/sda3 to /dev/md1 as 0
mdadm: /dev/md1 assembled from 2 drives - not enough to start the array.

This should have worked.  I suspect your mdadm is one of the buggy ones 
for forced assembly.

Download and compile latest mdadm and do this again.  (Newer mdadm works 
on older kernels.)

Regards,

Phil