On Tue, Jan 30, 2007 at 06:41:25PM +0100, Roch - PAE wrote: > I think I got the point. Mine was that if the data travels a > single time toward the storage and is corrupted along the > way then there will be no hope of recovering it since the > array was given bad data. Having the data travel twice is a > benefit for MTTDL.
Well, this is certainly true, so I missed your point :) Mirroring would help. A mirror with RAID-Z members would only double the I/O and still provide for combinatorial reconstruction when the errors arise from bit rot on the rotating rust or on the path from the RAID HW to the individual disks, as opposed to on the path from the host to the RAID HW. Depending on the relative error rates this could be a useful trade-off to make (plus, mirroring should halve access times while RAID-Z, if disk heads can be synchronized and the disks have similar geometries, can provide an N multiple increase in bandwidth, though I'm told that disk head synchronization is no longer a common feature). Nico -- _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
