On 02/09/11 11:41 AM, Colin Eby wrote: I don't believe that trying to do integrity measures at the wrapper level will work well. Even if you checksum blocks, and can recover at a block level, you don't know what the recoverable boundaries are. If the payload is a compressed bitstream (that is not designed for recoverability), then no matter what chunk-level recovery is done by the wrapper or transport, you can't recover anything beyond the first damaged bit. HOWEVER, if the file never leaves a high-integrity environment (like ZFS) during its lifetime, the data format itself can be as fragile as you like. All the error detection and healing is done at a layer UNDER the file (in ZFS' case, redundant vdev). That's a fine approach but clearly only possible for tightly controlled situations (and not much good for remote file servers using ordinary protocols, because the network is relatively unreliable). I'm not sure I understand what this adds to recoverability. Can you explain another way? I guess my point is that eventually you have to design the payload for recoverability. On the other hand... backups. :) --Toby