> 
> when a (centos6) raid rebuilds, is that logged somewhere?  where?
> 
> 
> ...has been rebooting a lot lately (see last listing below).  Also there
> > was the raid rebuild this morning around 9:30 to 11:30...


It is not about CentOS. You mean "Linux (software) RAID" here. It would be in
/var/log/messages and /var/log/syslog. In messages you will see that it started
rebuilding.

You can trigger a rebuild yourself. Suppose you have a RAID with 2 devices:
/dev/sdc6 /dev/sdc7 under /dev/md0.

mdadm /dev/md0 --fail /dev/sdc6
mdadm /dev/md0 --remove /dev/sdc6
mdadm /dev/md0 --add /dev/sdc6

This will remove the first partition and then add it back. IT will rebuild
that partition, depending on what mirroring RAID it is. RAID0 will just fail
the filesystem.

Now look in /proc/mdstat for info and progress:

cat /proc/mdstat

If you look in /var/log/messages you will see the logs of the events. I would
open a terminal and monitor the file before doing the above. Do this:

tail -f /var/log/messages

This will do.