RAID 1 disappears if sdb is removed

Hi, I'm having some issues with redundancy not working as it should with my RAID 1 setup. I'm running a fresh install of OMV 4.1.8 and as storage drives I have a WD RED 4TB (sda) and a Seagate Barracuda 3TB (sdb).

Today I noticed, by accident, that if sdb is removed then the entire RAID disappears and the File System status shows that md0 is missing. sda still shows up in 'Disks' but not in 'File Systems' This, of course, is not how RAID 1 should work and it means that if I lose the Seagate drive then my RAID is apparently lost. This is also bad because the Seagate is the older drive and it has a reputation for failing.

When both drives are connected the RAID works as it should and the status is 'Clean' with both drives showing up in 'Disks' and 'RAID management'. But I noticed that sda does *not* show up in 'File Systems' even when both drives are connected and the RAID is working normally. I'm guessing that's part of the issue why my RAID disappears if sdb is removed... I've attached a screenshot of what it looks like when both drives are connected and RAID is working.

Any ideas? Thanks in advance!

Zitat von votdev

Check

Bash

# cat /proc/mdstat

It surely shows you a degraded RAID.

I think you misunderstand how MDADM RAID works. Please check the kernel documentation about MDADM for more information.

Here's the output of cat /proc/mdstat, doesn't this mean that the RAID is ok?:

md0 : active raid1 sdb2[0] sda2[2]      2929765240 blocks super 1.2 [2/2] [UU]

And here's the output of mdadm --detail /dev/md0:

/dev/md0:
        Version : 1.2
  Creation Time : Thu Mar 10 21:14:15 2016
     Raid Level : raid1
     Array Size : 2929765240 (2794.04 GiB 3000.08 GB)
  Used Dev Size : 2929765240 (2794.04 GiB 3000.08 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent


    Update Time : Thu Jun 14 10:22:49 2018
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0


           Name : :0  (local to host)
           UUID : 782d7526:40efb178:b7926e6d:deed1e09
         Events : 2298267


    Number   Major   Minor   RaidDevice State
       0       8       18        0      active sync   /dev/sdb2
       2       8        2        1      active sync   /dev/sda2

Could the reason for sda not showing up in 'File System' be because the RAID was created on another NAS (proprietary 2-bay NAS box NSA325-V2 running linux by Zyxel)? I didn't notice until now that both drives have 487M partitions outside of the RAID array, sda1 is swap and sdb1 is ext2.

In any case I need the array to work even if the Seagate, sdb, fails... Should I just delete and recreate the RAID 1 array from within OMV and use all space for the array or is there any other way I could fix this?

~# lsblk -o NAME,SIZE,FSTYPE,TYPE,MOUNTPOINT
NAME          SIZE FSTYPE            TYPE  MOUNTPOINT
sda           3.7T                   disk
├─sda1        487M swap              part
└─sda2        3.7T linux_raid_member part
  └─md0       2.7T ext4              raid1 /srv/dev-disk-by-id-md-name-Vault-0
sdb           2.7T                   disk
├─sdb1        487M ext2              part
└─sdb2        2.7T linux_raid_member part
  └─md0       2.7T ext4              raid1 /srv/dev-disk-by-id-md-name-Vault-0

Tagging this as resolved, I ended up wiping the drives and recreating the array. Now everything works as it's supposed to.