/proc/mdstat and mdadm -D display incorrect status when two NVMe devices are surprise removed

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Environment

SUSE Linux Enterprise Server 15 SP2

Situation

When two of three NVMe devices are surprise removed from a RAID 5 MD array,
the command cat/proc/mdstat displays the array status incorrectly as active.

Similarly, when the status of the MD RAID is queried using the mdadm -D /dev/mdN command,
the number of active and working devices displayed is two.

Resolution

This behaviour is working as designed from MD perspective.
Only the status of the array reported is incorrect however, when I/O operations are performed, I/O errors are observed as expected.

Cause

If more devices are removed than the current RAID level can sustain, MD will no longer update its status information (e.g. in /proc/mdstat).

Disclaimer

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