Bug#601198: mdadm: Does all that can be expected ...

[Scott Schaefer]

I am glad that you phrased your request "It would better if it managed
to say it failed doing the requested operation.".

Because it indeed did successfully perform the operation, exactly as
the output indicated.  That is, it DID indeed set the MD_DISK_FAULTY
attribute on the /dev/sdb2 device of the /dev/md0 array.

To be more precise, it set the attribute via ioctl() call to the
kernel 'md' driver. (~ lines 980-995 of Manage.c).

Unfortunately, (or rather, fortunately, for your data as well as
your blood pressure), the kernel 'md' driver, when receiving this
request, sets flag to initiate a recovery, or, if a recovery is
already in progress (as in your case),  sets flag for
MD_RECOVERY_RECOVER.

I have not attempted to understand all the possibilities in the
kernel driver.  However, it appears that, at least for RAID-1,
the FAULTY flag on the (sdb2) device is cleared when the recovery
completes, and the 'RECOVERY_RECOVER' finds nothing more to do.

At this point, I believe this a "won't fix" issue; one could
potentially ask for mdadm to do some before/after status-check
magic and "handle" this and other potential cases in some
"better" way.  Asking it to do so raises a great deal many more
problems than it solves.

OTOH, if you believe the bug can be closed .... :-)