I''ve been playing with offlining an external USB disk as a way of having a backup of a laptop drive. However when I online the device and scrub it I always get cksum errors. So I just build a v880 in the lab with a mirrored zpool. I offlined 2 disks that form the mirror and then created a new file system. Then onlined the other disks and started a scrub, again I get cksum errors: v4u-880m-gmp03 19 # zpool status pool: tank state: ONLINE status: One or more devices has experienced an unrecoverable error. An attempt was made to correct the error. Applications are unaffected. action: Determine if the device needs to be replaced, and clear the errors using ''zpool clear'' or replace the device with ''zpool replace''. see: http://www.sun.com/msg/ZFS-8000-9P scrub: scrub completed with 0 errors on Fri May 19 18:12:04 2006 config: NAME STATE READ WRITE CKSUM tank ONLINE 0 0 0 mirror ONLINE 0 0 0 c1t2d0 ONLINE 0 0 0 c1t4d0 ONLINE 0 0 1 mirror ONLINE 0 0 0 c1t3d0 ONLINE 0 0 0 c1t5d0 ONLINE 0 0 1 errors: No known data errors v4u-880m-gmp03 20 # I expected that the device would be brought online and resilvered (as it had claimed it was) cleanly without any errors. Is this not the expected behaviour? This message posted from opensolaris.org