I have a problem. I found similar threads all over the internet, but I thought it might be better if I ask one specific with this configuration. There is a ubuntu 18 machine with 5x 4tb. I think it is raid5 (I did not install it, and the person who did is no longer here). There was a restart of the machine and since that I cannot assemble the raid.

To not make things worse, first I cloned the disks using

dd if=/dev/sdb of=sdb.iso bs=128k --status=progress

for sdb to sdf.

The first hint at an error might be, that sdb had an I/O Error after about 3TB.

I mounted them as loop devices and tried to assemble them:

mdadm: Cannot assemble mbr metadata on /dev/loop1
mdadm: /dev/loop1 has no superblock - assembly aborted

This is the same error as with the actual devices in the beginning.

mdadm --examine /dev/loop2

gives me

   MBR Magic : aa55
Partition[0] :   4294967295 sectors at            1 (type ee)

This is exactly the same for all (loop) devices.

Also, assemble --force does not work.

Interestingly, if I use blkid, the result is:

/dev/sdb: PTUUID="1e34016b-9c4f-4c4d-a36d-50726c3df4b1" PTTYPE="gpt"
/dev/sdc: PTUUID="c4cd0051-37fc-4213-8e07-d63367040597" PTTYPE="gpt"
/dev/sdd: PTUUID="ed0aa999-48eb-45f3-9d92-a7b47d40d60a" PTTYPE="gpt"
/dev/sde: PTUUID="e8d707c1-55c0-493d-836e-58b55d922c35" PTTYPE="gpt"
/dev/sdf: PTUUID="8052a90c-140c-4ea1-a347-fd65109a97a6" PTTYPE="gpt"

I know from software raids that I created, that the TYPE should be "linux_raid_member".

I just noticed that in the kernel log, there are alot of events from 3 weeks ago like:

handle_parity_checks5: 327 callbacks suppressed
md0: mismatch sector in range 1911818256-1911818264

I read that if I use create it could just rewrite superblock data onto the drives. But for that I would need to know the parameters that were used when it was first created. Since it was not me, I don't know that. I would need to rely on defaults.

So, I guess I have two questions: Is there anything else I can try besides just recreating?

Is there some log where the creation parameters might be in?


  • those are partition tables? try losetup --partscan then loopXpY partition device instead. – frostschutz Jan 31 at 10:25
  • There appear to be no partitions. losetup --partscan /dev/loop1p1 says "no suitable(? I have it in german) device found. – Pythoneer Jan 31 at 10:31
  • I detached the loop devices and attached them again usign losetup -P, but still only loop1 etc. Now loop1 (sdb) shows as /dev/loop1: PTTYPE="PMBR" – Pythoneer Jan 31 at 11:06

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