On Fri, Aug 22, 2008 at 02:25:20PM -0400, Ross S. W. Walker wrote:
I don't think you can grow it without backing it up, destroying it, rebuilding it with 5 devices, then restoring.
You _can_... but it requires a newer kernel. See, for example,
http://linux-raid.osdl.org/index.php/Growing#Adding_partitions
Newer kernels have this option:
config MD_RAID5_RESHAPE bool "Support adding drives to a raid-5 array" depends on MD_RAID456 default y ---help--- A RAID-5 set can be expanded by adding extra drives. This requires "restriping" the array which means (almost) every block must be written to a different place.
This option allows such restriping to be done while the array is online.
But it seems this isn't available in the CentOS 4.6 kernel.