In response to: >> I don't see much similarity between mirroring and raidz other than >> that they both support redundancy.
Martin wrote: > A single parity device against a single data device is, in essence, mirroring. > For all intents and purposes, raid and mirroring with this configuration are > one and the same. > I would have to disagree with this. Mirrored data will have mulitple copies of the actual data. Any copy is a valid source for data access. Lose one disk and the other is a complete "original". A raid 3/4/5/6/z/z2 configuration will generate a mathematical value to restore a portion of the lost data one of the storage units in the stripe. A 2-disk raidz will have 1/2 of each disk's used space holding primary data interlaced with the other 1/2 holding a parity "reflection" of the data. Any time we access the parity representation, some computation will be needed to render the live data. This would have to add *some* overhead to the io. Craig Cory _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
