On Thu, 3 Jun 2010, David Dyer-Bennet wrote:
But is having a RAIDZ2 drop to single redundancy, with replacement starting instantly, actually as good or better than having a RAIDZ3 drop to double redundancy, with actual replacement happening later? The "degraded" state of the RAIDZ3 has the same redundancy as the "healthy" state of the RAIDZ2.
Mathematically, I am sure that raidz3 is better. Redundancy statistics are not the only consideration though. Raidz3 will write slower and resilver slower. If the power supply produces a surge and fries all the drives, then raidz3 wil not help more than raidz2. Once the probability of failure due to unrelated drive failures becomes small enough, other factors related to the system become the dominant ones. The power supply could surge, memory can return wrong data (even with ECC), the OS kernel can have a bug, or a tree can fall on the computer during a storm.
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
