modifying degraded raid 1 then re-adding other members is bad

From: Alexandre Oliva
Date: Tue Aug 08 2006 - 05:36:05 EST

Assume I have a fully-functional raid 1 between two disks, one
hot-pluggable and the other fixed.

If I unplug the hot-pluggable disk and reboot, the array will come up
degraded, as intended.

If I then modify a lot of the data in the raid device (say it's my
root fs and I'm running daily Fedora development updates :-), which
modifies only the fixed disk, and then plug the hot-pluggable disk in
and re-add its members, it appears that it comes up without resyncing
and, well, major filesystem corruption ensues.

Is this a known issue, or should I try to gather more info about it?

This happened with 2.6.18rc3-git[367] (not sure which), plus Fedora
development patches.

Alexandre Oliva
Secretary for FSF Latin America
Red Hat Compiler Engineer aoliva@{,}
Free Software Evangelist oliva@{,}
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