Ulrich Graef wrote: > You need not to wade through your paper... > ECC theory tells, that you need a minimum distance of 3 > to correct one error in a codeword, ergo neither RAID-5 or RAID-6 > are enough: you need RAID-2 (which nobody uses today). > > Raid-Controllers today take advantage of the fact that they know, > which disk is returning the bad block, because this disk returns > a read error. > > ZFS is even able to correct, when an error in the data exist, > but no disk is reporting a read error, > because ZFS ensures the integrity from root-block to the data blocks > with a long checksum accompanying the block pointers. > >
The Netapp paper mentioned by JZ (http://pages.cs.wisc.edu/~krioukov/ParityLostAndParityRegained-FAST08.ppt) talks about write verify. Would this feature make sense in a ZFS environment? I'm not sure if there is any advantage. It seems quite unlikely, when data is written in a redundant way to two different disks, that both disks lose or misdirect the same writes. Maybe ZFS could have an option to enable instant readback of written blocks, if one wants to be absolutely sure, data is written correctly to disk. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
