I need to upgrade a redhat server to RHEL 5.4 however it has a software raid mirror on it which I have never encountered before. The drives are /dev/sda and /dev/sdb and the mirror is /dev/md0. What I want to do is break the mirror, pull sdb for a backup if things go wrong, upgrade RHEL, test and if all is sweet put sdb back in to start mirroring again.
Here is what I was going to do:
1. Shutdown server
2. Pull sdb
3. Boot server
4. Upgrade RHEL (without touching partitions or filesystems)
6. Drop server
7. Replug sdb
8. Boot server
9. Run raidhotadd /dev/md0 /dev/sdb
Will that work? Will the drive start mirroring the new system?
Similarly will I be able to swap sda with sdb if things go pear shaped to rollback?