Hi Scott, You can't add devices to an existing raidz1 or raidz2 "stripe". And the reason you can't is precisely because of full-stripe -- but variable width -- writes that RAID-Z uses to avoid the RAID-5 write hole. Let's say you have a 4+2 raidz2 configuration and you're doing a bunch of 1 sector writes:
| P | P | D | P | P | D | | P | P | D | P | P | D | ... There may be several parity sectors per row so adding another column doesn't work. To expand your pool, just add another raidz2 vdev of 7 disks. You will be using two additional parity disks, but the number of parity disks you use for a given configuration should ideally depend on the fault domain for those disks (controllers, fans, etc). Adam On Wed, Jul 12, 2006 at 12:04:58PM -0700, Scott Roberts wrote: > I've been reading through the documentation on ZFS, and was hoping I could > get some clarification and make sure I'm reading everything right. > > I'm looking to build a NAS box, using sata drives in a double parity > configuration (i.e. raidz2). This is mainly for warehousing large video > files, so access speed and IOPS aren't terribly critical. I won't immediately > need all 15 drives online, so what I would like to do is be able to resize > the raid array. > > Is there any way to resize with ZFS? Or would the only way to do this be to > make one raidz2 with 7 drives, and then when I need to expand make another > raidz2 in the same pool. Obviously having two virtual devices in the pool > means losing 4 drives to parity instead of just two. > > ie start out with > zpool create tank raidz2 c1t1d0 c1t2d0 c1t3d0 c1t4d0 c2t1d0 c2t2d0 c2t3d0 > > and when i'm ready to expand use > zpool add tank raidz2 c2t4d0 c3t1d0 c3t2d0 c3t3d0 c3t4d0 c4t1d0 c4t2d0 > c4t3d0 > > Any and all comments are appreciated. > > > This message posted from opensolaris.org > _______________________________________________ > zfs-discuss mailing list > [email protected] > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss -- Adam Leventhal, Solaris Kernel Development http://blogs.sun.com/ahl _______________________________________________ zfs-discuss mailing list [email protected] http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
