We have hardware RAID5 storage array. We would like to expand the capacity by replacing the harddrives. What is the recommended method? I'm thinking just taking out a drive with higher capacity one and wait until it rebuilds the array and repeat this process until all the drives been replaced. Has anyone done this? If so, how long does this process take?

It won't work because the RAID5 is striped evenly across all the drives and the RAID set (LUN) size was determine on original installation. That is to say if you had 4 x 300 GB drives originally then your RAID 5 set size was approximately 900 GB (equivalent of one disk is used for parity). While you can replace each of the 300 GB drives with say 1 TB drives it wouldn't increase capacity of the RAID set because it has to keep the integrity of the set. So each 1 TB drive you install will only have 300 GB used for data or parity.

The best way to do this is to backup everything from the current RAID set, replace all the drives at once, build the new RAID set and then restore the backup to the new RAID set. (Unless of course your system has the capability to see two RAID sets at the same time - then you could just build the new one and copy from the old one at your leisure.)

MensaWater,
Thank you for the clarification. I know what I have to do now but can't stop dreading it.