Unable to re-assemble RAID1 using mdadm -- failed to run array, invalid argument

Question

I'm trying to assemble a RAID1 array using mdadm. I'd like to be able to debug this error, but I'm not sure where the error actually is, other than "Invalid Argument".

Here's the main log. I can't tell what the error is, other than "Invalid Argument". It was working before after multiple reboots, but now on this reboot it doesn't work.

> mdadm --assemble --scan
mdadm: looking for devices for /dev/md1
mdadm: UUID differs from /dev/md/0.
mdadm: no RAID superblock on /dev/sdi
mdadm: UUID differs from /dev/md/0.
mdadm: no RAID superblock on /dev/sdh
mdadm: UUID differs from /dev/md/0.
mdadm: no RAID superblock on /dev/sdg
mdadm: no RAID superblock on /dev/md/0
mdadm: /dev/sdi1 is identified as a member of /dev/md1, slot 1 replacement.
mdadm: /dev/sdh1 is identified as a member of /dev/md1, slot 1.
mdadm: /dev/sdg1 is identified as a member of /dev/md1, slot 0.
mdadm: added /dev/sdh1 to /dev/md1 as 1 (possibly out of date)
mdadm: added /dev/sdi1 to /dev/md1 as 1 (possibly out of date) replacement
mdadm: added /dev/sdg1 to /dev/md1 as 0
mdadm: failed to RUN_ARRAY /dev/md1: Invalid argument

Here's what I don't totally understand. It's building /dev/md1, so why does it keep talking about the UUID for /dev/md0?

My mdadm.conf is:

#DEVICE partitions containers

# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes

# automatically tag new arrays as belonging to the local system
HOMEHOST <system>

# instruct the monitoring daemon where to send mail alerts
MAILADDR [email protected]

# definitions of existing MD arrays
#these are commented for some reason
#ARRAY /dev/md/1  metadata=1.2 UUID=450cec12:5c8a7248:3c93a59e:11ddc20e name=b:1
#ARRAY /dev/md/0  metadata=1.2 UUID=aa81a619:c1913636:1b48fbc0:11328059 name=b:0

# This file was auto-generated on Tue, 28 Jan 2020 20:33:10 -0500
# by mkconf $Id$
ARRAY /dev/md/0 metadata=1.2 name=b:0 UUID=aa81a619:c1913636:1b48fbc0:11328059
ARRAY /dev/md1 metadata=1.2 name=t:1 UUID=90370f2d:ca2757ed:46ff3b47:c8df472f

Did I edit something in my mdadm.conf a while back to make this not work? Like, /dev/md/1 is commented out (is that okay?).

Answer 1

The problem here was kinda weird. I had a spare hard drive with the RAID that mdadm detected as having bad blocks. The way I found out what was happening was the following:

mdadm --examine /dev/md1 /dev/sdd1 /dev/sdb1 /dev/sde1

/dev/sdd1:
   ...
   Creation Time : Sat Feb  1 12:05:48 2020
   Raid Level : raid1
   Raid Devices : 2
   ...
   Bad Block Log : 512 entries available at offset 72 sectors
   ...
   Device Role : Active device 0
   Array State : AA ('A' == active, '.' == missing, 'R' == replacing)


/dev/sdb1:
    ...
  Bad Block Log : 512 entries available at offset 72 sectors
    ...


   Device Role : Active device 1
   Array State : AA ('A' == active, '.' == missing, 'R' == replacing)


/dev/sde1:
         ...
  Bad Block Log : 512 entries available at offset 72 sectors - bad blocks present.
  ..
   Device Role : Replacement device 1
   Array State : AA ('A' == active, '.' == missing, 'R' == replacing)

Upon further reflection, the error message I got was extremely unhelpful, given what was the problem.

When I removed /dev/sde from the computer, and unmounted / stopped and remounted everything, I had to --add /dev/sdb1 back, then it did one of those rebuild processes (was very quick), then it worked.