Messages in this thread | | | Date | Sun, 12 Jan 2014 14:52:54 +0200 | From | Sagi Grimberg <> | Subject | Re: [PATCH 09/14] target/configfs: Expose protection device attributes |
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On 1/12/2014 2:43 PM, Martin K. Petersen wrote: >>>>>> "Sagi" == Sagi Grimberg <sagig@dev.mellanox.co.il> writes: >>> The IP checksum is only supported by DIX between OS and initiator, >>> not by the target. I guess we could signal to the initiator via a >>> vendor-private VPD that IP checksum is supported directly. But now >>> what we have hardware-accelerated T10 CRC I don't think it's a big >>> deal. > Sagi> shouldn't it stick around if it is not deprecated yet, the > Sagi> transport is required to support ip-csum->CRC conversion anyhow. > > SBC mandates that the guard tag on the wire and on the target device be > the T10 CRC. The IP checksum is a DIX-optimization for application-HBA > exchanges. The only place you should support the IP checksum is in the > initiator.
Right.
> Note that you could conceivably do a T10 CRC to IP checksum conversion > on writes received by the target and store the IP checksum on disk. And > then convert back to T10 CRC when the data is eventually read. But it > makes no sense to do that given that you will have to do the T10 CRC > calculation regardless. Even if the backing store is DIX-capable and > supports the IP checksum. >
I agree, but for backstore DIF (SW) emulation it will make sense.
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