On Fri, Jan 26, 2007 at 11:05:17AM -0800, Ed Gould wrote: > On Jan 26, 2007, at 9:42, Gary Mills wrote: > >How does this work in an environment with storage that's centrally- > >managed and shared between many servers? > > It will work, but if the storage system corrupts the data, ZFS will be > unable to correct it. It will detect the error. > > 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.
Our Netapp does double-parity RAID. In fact, the filesystem design is remarkably similar to that of ZFS. Wouldn't that also detect the error? I suppose it depends if the `wrong sector without notice' error is repeated each time. Or is it random? > I would suggest exporting two LUNs from your central storage and let > ZFS mirror them. You can get a wider range of space/performance > tradeoffs if you give ZFS a JBOD, but that doesn't sound like an > option. That would double the amount of disk that we'd require. I am actually planning on using two iSCSI LUNs and letting ZFS stripe across them. When we need to expand the ZFS pool, I'd like to just expand the two LUNs on the Netapp. If ZFS won't accomodate that, I can just add a couple more LUNs. This is all convenient and easily managable. -- -Gary Mills- -Unix Support- -U of M Academic Computing and Networking- _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
