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I have somehow managed to corrupt my RAID 5 array. I am using Ubuntu 24.04, and my existing RAID5 array is on 3 x 240Gb SSDs, and my OS is on a 120Gb SSD. As far as I can tell the 3 raid discs are OK (I have checked using smartctl and badblocks - no errors reported). The Disks utility shows the disks as being members of a Raid.

If I issue the command sudo mdadm --assemble --force --run --verbose /dev/md0 /dev/sdb /dev/sdc /dev/sdd I get the following response:

mdadm: looking for devices for /dev/md0
mdadm: /dev/sdb is identified as a member of /dev/md0, slot 0.
mdadm: /dev/sdc is identified as a member of /dev/md0, slot 2.
mdadm: /dev/sdd is identified as a member of /dev/md0, slot 1.
mdadm: added /dev/sdd to /dev/md0 as 1
mdadm: added /dev/sdc to /dev/md0 as 2
mdadm: added /dev/sdb to /dev/md0 as 0
mdadm: failed to RUN_ARRAY /dev/md0: Invalid argument

I don't understand the last line of the output - anyone?

Several times in the past when I have reinstalled my Ubuntu OS, all I have had to do to recover the Raid was to use mdadm --assemble (can't remember the full syntax I used) and that worked OK. So rather than reinstalling the OS I purge removed mdadm with apt, rebooted, updated and upgraded with apt, and reinstalled mdadm. As a result I no longer have outputs from cat /proc/mdstat, or a valid mdadm.conf file - sorry. Needless to say that didn't work. I tried using mdadm --build but it complained about not being able to build a level 5 raid - don't know why - anyone?

I don't want to go down the road of using mdadm --create because (I think) that will blow away the raid and create a new one. This would be disastrous for me, I need to get back my existing array even if it is in a degraded state so that I can backup the data and recreate it. Can anybody help save my sanity, please?

Regards, Stuart

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  • dmesg after mdadm --assemble? mdadm --examine? Commented Aug 22, 2024 at 9:14
  • are those the original disks or did you change one (and was it working before of course)? Using the entire disk like /dev/sdx to create a raid array can bring some problems if one of the disk in the group does not have the exact same number of sectors. Commented Aug 22, 2024 at 10:20
  • I have updated the question with dmesg output from mdadm --assemble Commented Aug 23, 2024 at 18:08
  • In response to darxmurf, these are the original disks (identical make and model) and to my knowledge have not cause a problem until now. Having said that, a few weeks ago I had a problem with the same initial symptoms - I could not log into the Ubuntu GUI because my /home directory is on my RAID (at the time I did not know the RAID might have been a problem). At that time I booted the machine into a previous kernel, that seemed OK, so I tried a normal boot and that was OK. Strange, but I thought no more of it. Commented Aug 23, 2024 at 18:13

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