Madison Kelly <[EMAIL PROTECTED]> writes: > Without it, specially in a failure state, the performance can collapse as > the CPU performs all that extra math.
It's really not the math that makes raid 5 hurt. It's that in order to calculate the checksum block the raid controller needs to read in the existing checksum block and write out the new version. So every write causes not just one drive seeking and writing, but a second drive seeking and performing a read and a write. The usual strategy for dealing with that is stuffing a huge nonvolatile cache in the controller so those reads are mostly cached and the extra writes don't saturate the i/o throughput. But those kinds of controllers are expensive and not an option for software raid. -- greg ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly