Bob Friesenhahn wrote: > On Tue, 22 Dec 2009, Marty Scholes wrote: > > > > That's not entirely true, is it? > > * RAIDZ is RAID5 + checksum + COW > > * RAIDZ2 is RAID6 + checksum + COW > > * A stack of mirror vdevs is RAID10 + checksum + > COW > > These are layman's simplifications that no one here > should be > comfortable with.
Well, ok. They do seem to capture the essence of what the different flavors of ZFS protection do, but I'll take you at your word. We do seem to be spinning off on a tangent, tho. > Zfs borrows proven data recovery technologies from > classic RAID but > the data layout on disk is not classic RAID, or even > close to it. > Metadata and file data are handled differently. > Metadata is always > uplicated, with the most critical metadata being > strewn across > multiple disks. Even "mirror" disks are not really > mirrors of each > other. I am having a little trouble reconciling the above statements, but again, ok. I haven't read the official RAID spec, so again, I'll take you at your word. Honestly, those seem like important nuances, but nuances nonetheless. > Earlier in this discussion thread someone claimed > that if a raidz disk > was lost that the pool was then just one data error > away from total disaster That would be me. Let me substitute the phrase "user data loss in some way, shape or form which disrupts availability" for the words "total disaster." Honestly, I think we are splitting hairs here. Everyone agrees that RAIDZ takes RAID5 to a new level. -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
