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Message-ID: <1389640930.5567.441.camel@haakon3.risingtidesystems.com>
Subject: Re: [PATCH 13/14] target/rd: Add DIF protection into rd_execute_rw
From: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
To: Sagi Grimberg <sagig@dev.mellanox.co.il>
Cc: Sagi Grimberg <sagig@mellanox.com>,
        "Nicholas A. Bellinger" <nab@daterainc.com>,
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        Christoph Hellwig <hch@lst.de>, Hannes Reinecke <hare@suse.de>,
        Or Gerlitz <ogerlitz@mellanox.com>
Date: Mon, 13 Jan 2014 11:22:10 -0800
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On Sun, 2014-01-12 at 13:53 +0200, Sagi Grimberg wrote:
> <SNIP>
> 
> >> I wander how we can skip  sbc_dif_verify_xxxx if the transport already
> >> offloaded DIF verify.
> >> I think that the transport should signal the core layer that it is able
> >> to offload DIF (ADD/STRIP/PASS/VERIFY), in which case the core should
> >> turn off the backstore DIF verify emulation to sustain performance.
> > So IBLOCK + PSCSI backends will need to be a non interleaved protection
> > PASS for fast path operation, and backend protection emulation is
> > reserved for RAMDISK and perhaps a special FILEIO full emulation mode.
> 
> But can't we avoid that if transport already verified? This will kill 
> performance.
> 

Sure, this will end up being configurable per backend if the fabric does
a CHECK + STRIP, or CHECK + PASS.

--nab



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