On Fri, 2007-10-05 at 09:40 -0300, Toby Thain wrote: > How far would that compromise ZFS' #1 virtue (IMHO), end to end > integrity?
Speed sells, and speed kills. If the offload were done on the HBA, it would extend the size of the "assumed correct" part of the hardware from just the CPU+memory to also include the offload device and all the I/O bridges, DMA widgets, etc., between it and memory. This is already the case for the TCP checksum offloads commonly performed in network cards, and, yes, people get bitten by it occasionally. An analysis of packets with bad tcp checksums i'm familiar with showed a fair number which showed patterns consistent with a DMA hiccup (repeated words or cache lines); those glitches on a system with checksum offload would turn into data corruption. See "When The CRC and TCP Checksum Disagree", http://www.sigcomm.org/sigcomm2000/conf/paper/sigcomm2000-9-1.pdf - Bill _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
