md0 not mounting on boot

[Kevin Seise]

I am running Buster with 4.11.0-1-amd64 on a system which has a soft raid device running on RAID 5. The device is not loaded on boot and therefore not mounting critical data files. From what I can tell, it looks like it is related to hte way that systemd handles the RAID, but I can't find any solutions. Can anyone help?
/etc/fstab says this for the drive in question:

UUID=721a889f:84c8047f:bce60417:66216eed /data ext4 nofail,defaults 0 2

[acewiza]

What does /etc/mdadm/mdadm.conf say?

[Kevin Seise]

Here is what us shows:
# cat /etc/mdadm/mdadm.conf
# mdadm.conf
#
# !NB! Run update-initramfs -u after updating this file.
# !NB! This will ensure that initramfs has an uptodate copy.
#
# Please refer to mdadm.conf(5) for information about this file.
#

# by default (built-in), scan all partitions (/proc/partitions) and all
# containers for MD superblocks. alternatively, specify devices to scan, using
# wildcards if desired.
#DEVICE partitions containers

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

# instruct the monitoring daemon where to send mail alerts
MAILADDR root

# definitions of existing MD arrays
ARRAY /dev/md/0 metadata=1.2 UUID=721a889f:84c8047f:bce60417:66216eed name=blackbox:0
spares=1

[acewiza]

What's returned by:

Code: Select all

mdadm --detail /dev/md0

[Kevin Seise]

Code: Select all

# mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Sun Oct  6 10:02:05 2013
     Raid Level : raid5
     Array Size : 1952382976 (1861.94 GiB 1999.24 GB)
  Used Dev Size : 1952382976 (1861.94 GiB 1999.24 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Sun Jul 30 22:56:24 2017
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

           Name : blackbox:0  (local to host blackbox)
           UUID : 721a889f:84c8047f:bce60417:66216eed
         Events : 3862

    Number   Major   Minor   RaidDevice State
       0       8       66        0      active sync   /dev/sde2
       1       8       34        1      active sync   /dev/sdc2

[acewiza]

Only 2 devices for a RAID5? That's a new one on me...

[Kevin Seise]

That seems to be the key issue. One of my array disks was being mounted incorrectly on the /dev/md0 point. I removed it, rebuild the array, and it seems to be fine now. For some reason md0 us now md127, but I can live with that. One of my drives has disappeared though. I have drives sda,b,c,e. No d drive. That is a weird one that I have to investigate. Thank you for pointing me in the right direction.

[acewiza]

I had a similar issue recently. Not sure what mechanism was at work causing this behavior, but saw the same md127 result. I put it down to a flaky SCSI bus.

MDADM is great when it's working, tricky to troubleshoot when it's not.

[Kevin Seise]

It is not a faulty SCSI bus. Somehow the naming process with mdadm vs. kernel building of the RAID has changed. It is consistent though, so I can work with it. I am still researching how to get it back to md0.