On Fri, 25 Jul 2008, Brandon High wrote: > > Mirroring will provide a boost on reads, since the system to read from > both sides of the mirror. It will not provide an increase on writes, > since the system needs to wait for both halves of the mirror to > finish. It could be slightly slower than a single raid5.
Is anything really slower than a RAID5? For absolute fastest performance with least IOPS tax on the disks, the ideal configuration (for performance) is load-shared mirror pairs. As Adam Leventhal points out, there is a rather severe IOPS tax from using raidz or raidz2. Raidz saves disk space, and raidz2 saves disk space plus offers much more VDEV reliability. In today's market, IOPS are much more expensive than raw I/O throughput or raw storage space. Disk drives have hit the wall in terms of seek times and rotational latency but still have quite a ways to go in terms of data rates. Don't consume your precious IOPS unless you have to. I am not sure if ZFS really has to wait for both sides of a mirror to finish, but even if it does, if there are enough VDEVs then ZFS can still proceed with writing. Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
