Was poking around in syslog and maybe found a clue. First, booting with
the 4.19.0-9 kernel (raid isn't being mounted), I see this error:
May 12 07:37:13 server-pc systemd[1]: dev-md0.device: Job dev-md0.device/start timed out.
May 12 07:37:13 server-pc systemd[1]: Timed out waiting for device /dev/md0.
May 12 07:37:13 server-pc systemd[1]: Dependency failed for /mnt/md0.
May 12 07:37:13 server-pc systemd[1]: mnt-md0.mount: Job mnt-md0.mount/start failed with result 'dependency'.
May 12 07:37:13 server-pc systemd[1]: Startup finished in 11.398s (kernel) + 1min 30.148s (userspace) = 1min 41.546s.
May 12 07:37:13 server-pc systemd[1]: dev-md0.device: Job dev-md0.device/start failed with result 'timeout'.
Later on, the array is being assembled as md127 I guess?
May 12 07:40:19 server-pc kernel: [ 11.049712] md/raid:md127: device sdk operational as raid disk 0
May 12 07:40:19 server-pc kernel: [ 11.049712] md/raid:md127: device sdg operational as raid disk 1
May 12 07:40:19 server-pc kernel: [ 11.049713] md/raid:md127: device sdi operational as raid disk 7
May 12 07:40:19 server-pc kernel: [ 11.049713] md/raid:md127: device sda operational as raid disk 11
May 12 07:40:19 server-pc kernel: [ 11.049713] md/raid:md127: device sdo operational as raid disk 12
May 12 07:40:19 server-pc kernel: [ 11.049714] md/raid:md127: device sdn operational as raid disk 13
May 12 07:40:19 server-pc kernel: [ 11.049714] md/raid:md127: device sdj operational as raid disk 8
May 12 07:40:19 server-pc kernel: [ 11.049714] md/raid:md127: device sdh operational as raid disk 3
May 12 07:40:19 server-pc kernel: [ 11.049715] md/raid:md127: device sdl operational as raid disk 4
May 12 07:40:19 server-pc kernel: [ 11.049715] md/raid:md127: device sdf operational as raid disk 9
May 12 07:40:19 server-pc kernel: [ 11.049715] md/raid:md127: device sdb operational as raid disk 2
May 12 07:40:19 server-pc kernel: [ 11.049716] md/raid:md127: device sdd operational as raid disk 6
May 12 07:40:19 server-pc kernel: [ 11.049716] md/raid:md127: device sde operational as raid disk 10
May 12 07:40:19 server-pc kernel: [ 11.049716] md/raid:md127: device sdc operational as raid disk 5
May 12 07:40:19 server-pc kernel: [ 11.050101] md/raid:md127: raid level 6 active with 14 out of 14 devices, algorithm 2
May 12 07:40:19 server-pc kernel: [ 11.078716] md127: detected capacity change from 0 to 48007829520384
Now, booting with 4.19.0-8 kernel (raid IS mounted)..... I don't get the
error about 'md0.device timing out' and notice how now, the array is
called md0?
May 12 07:42:08 server-pc kernel: [ 10.874912] md/raid:md0: device sdh operational as raid disk 3
May 12 07:42:08 server-pc kernel: [ 10.874912] md/raid:md0: device sdj operational as raid disk 8
May 12 07:42:08 server-pc kernel: [ 10.874912] md/raid:md0: device sdl operational as raid disk 4
May 12 07:42:08 server-pc kernel: [ 10.874913] md/raid:md0: device sdb operational as raid disk 2
May 12 07:42:08 server-pc kernel: [ 10.874913] md/raid:md0: device sdf operational as raid disk 9
May 12 07:42:08 server-pc kernel: [ 10.874913] md/raid:md0: device sdc operational as raid disk 5
May 12 07:42:08 server-pc kernel: [ 10.874914] md/raid:md0: device sde operational as raid disk 10
May 12 07:42:08 server-pc kernel: [ 10.874914] md/raid:md0: device sdd operational as raid disk 6
May 12 07:42:08 server-pc kernel: [ 10.874914] md/raid:md0: device sdg operational as raid disk 1
May 12 07:42:08 server-pc kernel: [ 10.874915] md/raid:md0: device sdk operational as raid disk 0
May 12 07:42:08 server-pc kernel: [ 10.874915] md/raid:md0: device sdi operational as raid disk 7
May 12 07:42:08 server-pc kernel: [ 10.874915] md/raid:md0: device sda operational as raid disk 11
May 12 07:42:08 server-pc kernel: [ 10.874915] md/raid:md0: device sdn operational as raid disk 13
May 12 07:42:08 server-pc kernel: [ 10.874916] md/raid:md0: device sdo operational as raid disk 12
May 12 07:42:08 server-pc kernel: [ 10.875303] md/raid:md0: raid level 6 active with 14 out of 14 devices, algorithm 2
May 12 07:42:08 server-pc kernel: [ 10.907815] md0: detected capacity change from 0 to 48007829520384
I'm fairly certain my array has always been md0. I guess that name change (from md127 to md0) is responsible for the failure?
Why is the -9 kernel trying to assemble my array as md127 while -8 uses the correct name (md0)?