On Sun, 15 Feb 2009, Robert Milkowski wrote:
Well, in most cases resilver in ZFS should be quicker than resilver in a disk array because ZFS will resilver only blocks which are actually in use while most disk arrays will blindly resilver full disk drives. So assuming you still have plenty unused disk space in a pool then zfs resilver should take less time.
It is reasonable to assume that storage will eventually become close to full. Then the user becomes entrapped by their design. Adding to the issues is that as the ZFS pool ages and becomes full, it becomes slower as well due to increased fragmentation, and this fragmentation slows down resilver performance.
We have heard here from people who based their pool on a mirror of large multi-terrabyte LUNs. This seemed to initially work ok but later on (to their dismay) they discovered that it would take several days or a week to resilver one of the LUNs. The most severe cases were when the huge LUN is actually a ZFS volume exported by iSCSI from a server (e.g. a whole Thumper). When one of the LUNs gets rebooted, it takes quite a long time for ZFS to catch it up, and possibly it (or its peer) will be rebooted again in the mean-time.
Bob ====================================== Bob Friesenhahn bfrie...@simple.dallas.tx.us, 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
