> On Sun, Jul 6, 2008 at 3:46 PM, Ross [EMAIL PROTECTED] wrote: > For your second one I'm less sure what's going on: > ... . The problem is that a two disk raid-z makes no sense. > Traditionally this level of raid needs a minimum of three disks to work. > I suspect ZFS may be interpreting raid-z as requiring one parity > drive, in which case this will effectively mirror the drives, but > without the read performance boost that mirroring would give you.
> The way zpool create works is that you can specify > raid or mirror sets, but that if you list a bunch of > these one after the other, it simply strips the data > across them. > I read somewhere, a long time ago when ZFS documentation were still > mostly speculation, that raidz will use "mirroring" when the amount of > data to be written is less than what justifies 2+parity. Eg in stead > of 1+parity, you get mirrored data for small writes, and essentially > raid-5 for big writes, with writes with intermediate sizes having raid > 5 - like spread of blocks across disks but using fewer than the total > nr of disks in the set. > If that still holds true, then a raidz of 2 disks is probably just a > mirror? Exactly. I wish we could either have the commands do as we ask _OR_ tell us that we made an error instead of doing whatever they think we wanted. The displayed result can also being confusing (to us newcomers) and since the filesystem (ZFS) is new (and under development) there is bound to be some confusion. I tried a few configurations of raid / mirroring and was using IOZone to test them when things drew to a crawl and eventually (many hours later) crashed. I've now installed snv_93 (so some prior things may not apply) and will be testing that now. System load is definitely going to factor into my configuration choice. Thanks for all the replies (this post seems to go to the zfs-discuss@opensolaris.org mailing list but posts there don't seem to end up here). Sincerely, Rob This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
