On Thu, 3 Jun 2010, David Dyer-Bennet wrote:
In an 8-bay chassis, there are other concerns, too. Do I keep space open for a hot spare? There's no real point in a hot spare if you have only one vdev; that is, 8-drive RAIDZ3 is clearly better than 7-drive RAIDZ2 plus a hot spare. And putting everything into one vdev means that for any upgrade I have to replace all 8 drives at once, a financial problem for a home server.
It is not so clear to me that an 8-drive raidz3 is clearly better than 7-drive raidz2 plus a hot spare. From a maintenance standpoint, I think that it is useful to have a spare drive or even an empty spare slot so that it is easy to replace a drive without needing to physically remove it from the system. A true hot spare allows replacement to start automatically right away if a failure is detected.
With only 8-drives, the reliability improvement from raidz3 is unlikely to be borne out in practice. Other potential failures modes will completely drown out the on-paper reliability improvement provided by raidz3.
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
