On Wed, 31 Jul 2013 16:30:34 +0200 Francis Moreau [off-list ref]
wrote:

Hello list,

I thought that using "--takeover" would hint mdmon to replace existing
mdmon process, and therefore the old one would exit somehow.

However after several "mdmon --takeover" I can see this:
 $ ps aux | grep dmon
root       233  0.0  0.2  80388 10752 ?        SLsl 14:02   0:00 @dmon
--offroot md127
root      3326  0.0  0.2  14920 10820 ?        SLsl 15:16   0:00 mdmon
--takeover md127
root      3343  0.0  0.2  14920 10820 ?        SLsl 15:17   0:00 mdmon
--takeover md127

Is this expected ?

Thanks.

Nope.  That's not expected.

mdmon should send SIGTERM to the old mdmon and then wait for it to exit.

If the new and old mdmon were compiled different and look for the pid file in
different directories that might explain what you see.

If you compile mdadm from source it will use /run/mdadm.  However if your
distro doesn't have /run the the distro-provided mdadm will be compiled
differently.

It is safe to kill the old mdmons once a new one is running, but you should
probably find out what the incompatibility is...

NeilBrown