Thank you to all who responded. This response in particular was very helpful and I think I will stick with my current zpool configuration (choice "a" if you're reading below). I primarily host VMware virtual machines over NFS from this server's predecessor and this server will be doing the same thing. I think the 6 x 2-way mirror configuration gives me the best mix of performance and fault tolerance.
Regards, Chris Dunbar On Mar 19, 2010, at 5:44 PM, Erik Trimble wrote: > Chris Dunbar - Earthside, LLC wrote: > > Hello, > > > > After being immersed in this list and other ZFS sites for the past few > > weeks I am having some doubts about the zpool layout on my new server. It's > > not too late to make a change so I thought I would ask for comments. My > > current plan to to have 12 x 1.5 TB disks in a what I would normally call a > > RAID 10 configuration. That doesn't seem to be the right term here, but > > there are 6 sets of mirrored disks striped together. I know that "smaller" > > sets of disks are preferred, but how small is small? I am wondering if I > > should break this into two sets of 6 disks. I do have a 13th disk available > > as a hot spare. Would it be available for either pool if I went with two? > > Finally, would I be better off with raidz2 or something else instead of the > > striped mirrored sets? Performance and fault tolerance are my highest > > priorities. > > > > Thank you, > > Chris Dunbar > There's not much benefit I can see to having two pools if both are using > the same configuration (i.e all mirrors or all raidz). There are reasons > to do so, but I don't see that they would be of any real benefit for > what you describe. A Hot spare disk can be assigned to multiple pools > (often referred to as a "global" hot spare) > > Preferences for raidz[123] configs is to have 4-6 data disks in the vdev. > > Realistically speaking, you have several different (practical) > configurations possible, in order of general performance: > > (a) 6 x 2-way mirrors + 1 pool hot spare -> 9TB usable > (b) 4 x 3-ways mirrors + 1 pool hot spare -> 6TB usable > (c) 1 6-disk raidz + 1 7-disk raidz -> 16.5TB usable > (d) 2 6-disk raidz + 1 pool hot spare -> 15TB usable > (e) 1 6-disk raidz2 + 1 7-disk raidz2 -> 13.5TB usable > (f) 2 6-disk raidz2 + 1 pool hot spare -> 12TB usable > (g) 1 6-disk raidz3 + 1 7-disk raidz3 -> 10.5TB usable > (h) 1 13-disk raidz3 -> 15TB usable > > Given the size of your disks, resilvering is likely to have a > significant time problem in any RAIDZ[123] configuration. That is, > unless you are storing (almost exclusively) very large files, resilver > time is going to be significant, and can potentially be radically higher > than a mirrored config. > > The mirroring configs will out-perform raidz[123] on everything except > large streaming write/reads, and even then, it's a toss-up. > > Overall, the (a), (d), and (f) configurations generally offer the best > balance of redundancy, space, and performance. > > Here's the chances to survive disk failures (assuming hot spares are > unable to be used; that is, all disk failures happen in a short period > of time) - note that all three can always survive a single disk failure: > > (a) 90% for 2, 73% for 3, 49% for 4, 25% for 5. > (d) 55% for 2, 27% for 3, 0% for 4 or more > (f) 100% for 2, 80% for 3, 56% for 4, 0% for 5. > > > Depending on your exact requirements, I'd go with (a) or (f) as the best > choices - (a) if performance is more important, (f) if redundancy > overrides performance. > > -- > Erik Trimble > Java System Support > Mailstop: usca22-123 > Phone: x17195 > Santa Clara, CA > > eSoft SpamFilter Training Tool > Train as Spam > Blacklist for All Users > Whitelist for All Users
_______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
