Messages in this thread | | | Date | Mon, 19 Nov 2012 12:38:18 +0100 | From | Paolo Bonzini <> | Subject | Re: [PATCH 3/3] target/iblock: Add WRITE_SAME w/ UNMAP=0 emulation support |
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Il 15/11/2012 21:01, Elliott, Robert (Server Storage) ha scritto: > WRITE SAME always has a payload, regardless of the UNMAP bit value. > > For WRITE SAME with UNMAP=0, it's extremely important; that's how > what to write is specified. > > For WRITE SAME with UNMAP=1, the device server is required to check > that the payload matches the data that is returned for unmapped LBAs. > lf LBPRZ=1 (read zeros for unmapped LBAs), that means checking that > the payload has all zeros. In sbc3r33, this rule is tucked away in > model section 4.7.3.4.3, not the command section 5.41.
Does that mean that LBPRZ=0, LPBWS=1 is practically an invalid combination? Because there's no real way for the device server to perform the check successfully.
Paolo
> I would like to change that rule (it's a nuisance and a performance > burden), but that's the current rule going into SBC-3 letter ballot. > > Changing WRITE SAME with UNMAP=1 to ignore the payload would provide > essentially the same functionality as changing the UNMAP command to > be mandatory, not just a hint; both approaches have been discussed.
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