Error message is during shutdown as in the original mail:
md: md125 stopped
Or close enough, I currently can't stop the system. The message is spammed as fast as possible at as it seems. Output of the commands is as follow: # cat /proc/mdstat Personalities : [raid1] md125 : active raid1 sda3[0] sdb1[1] 3756352512 blocks super 1.2 [2/2] [UU] bitmap: 2/28 pages [8KB], 65536KB chunk md126 : active raid1 sda5[0] sdb3[1] 58592256 blocks super 1.2 [2/2] [UU] bitmap: 1/1 pages [4KB], 65536KB chunk md127 : active raid1 sda4[0] sdb2[1] 73399296 blocks super 1.2 [2/2] [UU] bitmap: 1/1 pages [4KB], 65536KB chunk unused devices: <none> # mdadm --detail /dev/md125 /dev/md125: Version : 1.2 Creation Time : Sat Nov 19 14:58:50 2022 Raid Level : raid1 Array Size : 3756352512 (3.50 TiB 3.85 TB) Used Dev Size : 3756352512 (3.50 TiB 3.85 TB) Raid Devices : 2 Total Devices : 2 Persistence : Superblock is persistent Intent Bitmap : Internal Update Time : Fri Jan 6 11:21:50 2023 State : clean Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Consistency Policy : bitmap Name : arkham:home (local to host arkham) UUID : ad23388f:4e227a6c:2b3d141a:7a5f2338 Events : 9621 Number Major Minor RaidDevice State 0 8 3 0 active sync /dev/sda3 1 8 17 1 active sync /dev/sdb1 As I've said, I currently can't stop the system to see if it still happens. But I've seen it at least twice after the initial setup (and after the RAID had finished its initial sync).