Ed Gould wrote: > On Jan 26, 2007, at 12:13, Richard Elling wrote: >> On Fri, Jan 26, 2007 at 11:05:17AM -0800, Ed Gould wrote: >>> A number that I've been quoting, albeit without a good reference, >>> comes from Jim Gray, who has been around the data-management industry >>> for longer than I have (and I've been in this business since 1970); >>> he's currently at Microsoft. Jim says that the controller/drive >>> subsystem writes data to the wrong sector of the drive without notice >>> about once per drive per year. In a 400-drive array, that's once a >>> day. ZFS will detect this error when the file is read (one of the >>> blocks' checksum will not match). But it can only correct the error >>> if it manages the redundancy.
> Actually, Jim was referring to everything but the trunk. He didn't > specify where from the HBA to the drive the error actually occurs. I > don't think it really matters. I saw him give a talk a few years ago at > the Usenix FAST conference; that's where I got this information. So this leaves me wondering how often the controller/drive subsystem reads data from the wrong sector of the drive without notice; is it symmetrical with respect to writing, and thus about once a drive/year, or are there factors which change this? Dana _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
