I'm also seeing this on my trixie system. A number of other users have reported this same issue elsewhere, particularly users of OpenMediaVault after upgrading to OMV 8 (based on trixie)[1][2]. It appears to be a regression introduced in 84d969be8f6d8a345b75f558fad26e4f62a558f6 upstream[3], which was first included in 4.2+20230223-1. This was later fixed by 456c6bed0b9e0866c75f0f7c8579d5f4f3f3e966 upstream[4], which was first included in 4.5-1. So in theory at this point, only trixie is impacted by this anymore.
I tested applying 456c6bed0b9e0866c75f0f7c8579d5f4f3f3e966 onto the 4.4-11 sources on my trixie box (had to massage the patch a bit), and it appears to correct the issue. I didn't try updating to 4.5, though I would suspect that to work as well. --- [1]: https://forum.openmediavault.org/index.php?thread/58088-mdadm-devicedisappeared-event-detected-on-md-device-dev-md-md0-since-upgrade-to/ [2]: https://forum.openmediavault.org/index.php?thread/58015-md-email-every-morning/ [3]: https://github.com/md-raid-utilities/mdadm/commit/84d969be8f6d8a345b75f558fad26e4f62a558f6 [4]: https://github.com/md-raid-utilities/mdadm/commit/456c6bed0b9e0866c75f0f7c8579d5f4f3f3e966
