On Sun, 2 May 2010, Tonmaus wrote:
I am under the impression that exactly those were the considerations for both the ZFS designers to implement a scrub function to ZFS and the author of Best Practises to recommend performing this function frequently. I am hearing you are coming to a different conclusion and I would be interested in learning what could possibly be so highly interpretable in this.
The value of periodic scrub is subject to opinion. There are some highly respected folks on this list who put less faith in scrub because they believe more in MTTDL statistical models and less in the value of early detection (scrub == early detection). With a single level of redundancy, early detection is more useful since there is just one opportunity to correct the error and correcting the error early decreases the chance of a later uncorrectable error. Scrub will help repair the results of transient wrong hardware operation, or partial media failures, but will not keep a whole disk from failing.
Once the computed MTTDL for the storage configuration is sufficiently high, then other factors such as the reliability of ECC memory, kernel bugs, and hardware design flaws, become dominant. The human factor is often the most dominant factor when it comes to data loss since most data loss is still due to human error. Most data loss problems we see reported here are due to human error or hardware design flaws.
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
