On Wed, 17 Sep 2008, Scott Williamson wrote: > We are currently testing a 22 disk zpool with 2 11 1TB disk wide raidz2 > vdevs on a thumper and are seeing it preform very poorly. > > Why does this configuration increase the movement of disk heads?
Each write to a vdev causes a write to all the disks in that vdev. This means that the write consumes at least one IO from each of the involved disks. That write does not cause any activity in the non-involved vdevs. As a general rule, multi-user performance should improve linearly with the number of vdevs since each vdev contributes a disk's share of IOPS. However, in the special case where the vdevs are mirrors, the read performance can be doubled since the read may be done independently from each side of the mirror, thereby doubling the available read IOPS. Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ storage-discuss mailing list [email protected] http://mail.opensolaris.org/mailman/listinfo/storage-discuss
