A lot of people keep coming back to a post from 2006 I wrote about expanding a raid5 array. Although that post is still very much relevant 2 years is a looong time in the Linux kernel world, and things have moved on. Rather than use the information here you’re better off going to the Linux Raid wiki. This is very much an active and up to date resource for playing/creating and using Linux software raid and MDADM. It’s contains the thoughts and the resources of many people from the very interesting Linux Kernel raid mailing list.