[mythtv-users] CentOS vs Fedora, RAID vs LVM

[David Brodbeck]

Just realized I never answered the OP's original question.

mdadm --grow is supported, but only in a limited way.  In particular, 
reshaping a RAID 5 or RAID 6 array (e.g., adding more disks) is 
apparently only supported in kernel 2.6.21 and above.  CentOS 5 is using 
the 2.6.18 kernel.  So you'd have to build your own custom kernel to do 
it.  CentOS usually settles on one kernel version and then backports 
security and stability fixes for the life of the distribution.  This 
avoids a potentially disruptive kernel upgrade.