> I have a small question about the depth of scrub in a > raidz/2/3 configuration. > I'm quite sure scrub does not check spares or unused > areas of the disks (it > could check if the disks detects any errors there). > But what about the parity?
>From some informal performance testing of RAIDZ2/3 arrays, I am confident that >scrub reads the parity blocks and normal reads do not. You can see this for yourself with "iostat -x" or "zpool iostat -v" Start monitoring and watch read I/O. You will see regularly that a RAIDZ3 array will read from all but three drives, which I presume is the unread parity. Do the same monitoring while a scrub is underway and you will see all drives being read from equally. My experience suggests something similar is taking place with mirrors. If you think about it, having a scrub check everything but the parity would be a rather pointless operation. -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
