On Sat, Jun 6, 2009 at 12:54 PM, Ivan Voras<[email protected]> wrote: > Sorry to come into the discussion late, but I just want to confirm > something. > > The configuration below is a stripe of four components, each of which is > RAIDZ2, right? > > If, as was discussed later in the thread, RAIDZ(2) is more similar to > RAID3 than RAID5 for random performance, the given configuration can be > (very roughly, in the non-sequential access case) expected to deliver > performance of four drives in a RAID0 array?
According to all the Sun documentation, the I/O throughput of a raidz configuration is equal to that of a single drive. Hence their recommendation to not use more than 8 or 9 drives in a single raidz vdev, and to use multiple raidz vdevs. As you add vdevs, the throughput increases. We made the mistake early on of creating a 24-drive raidz2 vdev. Performance was not very good. And when we had to replace a drive, it spent over a week trying to resilver. But the resilver operation has to touch every single drive in the raidz vdev. :( We remade the pool using 3x 8-drive raidz2 vdevs, and performance has been great (400 MBytes/s write, almost 3 GBytes/s sequential read, 800 MBytes/s random read). -- Freddie Cash [email protected] _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[email protected]"
