On Thursday 10 December 2009, Matt lm7812@gmail.com wrote:
I have CentOS 4.x installed on a single 500GB SATA drive. Drive is about 10 percent used. I would like to migrate to software RAID 5 without reinstalling the OS. Was thinking 3 500GB drives. Is that possible or must I reinstall?
In theory you can create a 3-drive RAID-5 with a "missing drive", rsync your filesystems over, and then repartition and force the existing drive to rebuild in.
You can't boot off a RAID-5, so you'll need to put /boot on a separate partition, also preferably raid-1'd on at least 2 of the drives.
It's not terribly hard but it's possibly to mess up and nuke your good drive before you're ready, so you should have a full backup on yet another drive anyway, and if you have that you might as well just build up a new system on the 3 drives and then restore your old filesystems over it.