On Apr 15, 2008, at 11:18 AM, Bob Friesenhahn wrote: > On Tue, 15 Apr 2008, Keith Bierman wrote: >> >> Perhaps providing the computations rather than the conclusions >> would be more persuasive on a technical list ;> > > No doubt. The computations depend considerably on the size of the > disk drives involved. The odds of experiencing media failure on a > single 1TB SATA disk are quite high. Consider that this media > failure may occur while attempting to recover from a failed disk. > There have been some good articles on this in USENIX Login magazine. > > ZFS raidz1 and raidz2 are NOT directly equivalent to RAID5 and > RAID6 so the failure statistics would be different. Regardless, > single disk failure in a raidz1 substantially increases the risk > that something won't be recoverable if there is a media failure > while rebuilding. Since ZFS duplicates its own metadata blocks, it > is most likely that some user data would be lost but the pool would > otherwise recover. If a second disk drive completely fails, then > you are toast with raidz1. > > RAID5 and RAID6 rebuild the entire disk while raidz1 and raidz2 > only rebuild existing data blocks so raidz1 and raidz2 are less > likely to experience media failure if the pool is not full. > Indeed; but worked illustrative examples are apt to be more helpful than blanket pronouncements ;>
-- Keith H. Bierman [EMAIL PROTECTED] | AIM kbiermank 5430 Nassau Circle East | Cherry Hills Village, CO 80113 | 303-997-2749 <speaking for myself*> Copyright 2008 _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
