* On 28 Mar 2009, Peter Tribble wrote: > The choice of raidz1 versus raidz2 is another matter. Given that > you've already got raidz1, and you can't (yet) grow that or expand > it to raidz2, then there doesn't seem to be much point to having the > second half of your storage being more protected. > > If you were starting from scratch, then you have a choice between a > single raidz2 vdev and a pair of raidz1 vdevs. (Lots of other choices > too, but that is really what you're asking here I guess.)
I've had too many joint failures in my life to put much faith in raidz1, especially with 7 disks that likely come from the same manufacturing batch and might exhibit the same flaws. A single-redundancy system of 7 disks (gross) has too high a MTTDL for my taste. If you can sell yourself on raidz2 and the loss of two more disks' worth of data -- a loss which IMO is more than made up for by the gain in security -- consider this technique: 1. build a new zpool of a single raidz2; 2. migrate your data from the old zpool to the new one; 3. destroy the old zpool, releasing its volumes; 4. use 'zpool add' to add those old volumes to the new zpool as a second raidz2 vdev (see Richard Elling's previous post). Now you have a single zpool consisting of two raidz2 vdevs. The migration in step 2 can be done either by 'zfs send'ing each zfs in the zpool, or by constructing analogous zfs in the new zpool and rsyncing the files across in one go. -- -D. d...@uchicago.edu NSIT University of Chicago _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
