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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: iSCSI draft-07 PaddingWhat does a Fibre Channel driver do when the ULP wants to receive data into memory which is not a multiple of 4 bytes long? Eddy ----- Original Message ----- From: "Michael Schoberg" <michael_schoberg@cnt.com> To: <ips@ece.cmu.edu> Sent: Tuesday, July 24, 2001 11:13 AM Subject: RE: iSCSI draft-07 Padding > Yes, at the very least the spec should not allow padding on intermediate > ReadData/WriteData bursts. I can't think of a reason why one would want to > use odd length intermediate bursts, so hopefully it's safe to restrict it. > Padding the last burst still seems reasonable for easy CRC calculation. > > Setting a fixed size is optional. A minimum would avoid memory > fragmentation when working with memory descriptors. > > : -----Original Message----- > : From: Robert Snively [mailto:rsnively@Brocade.COM] > : Sent: Tuesday, July 24, 2001 8:34 AM > : To: ips@ece.cmu.edu > : Subject: RE: iSCSI draft-07 Padding > : > : > : Fibre Channel's approach to this problem is to prohibit padding > : for all transfers except the transfer that moves the last bytes > : in the last (or highest pointer value) burst of data. Intermediate > : bursts are required to end on 4-byte boundaries, regardless of > : tranfer order as allowed by EMDP. > : > : Bob > : > : ----- Original Message ----- > : From: "Michael Schoberg" <michael_schoberg@cnt.com> > : To: <ips@ece.cmu.edu> > : Sent: Friday, July 20, 2001 4:27 PM > : Subject: iSCSI draft-07 Padding > : > : > : > I couldn't find anything in the latest iSCSI spec > : (draft-07) that prevents > : > someone from issuing multiple padded PDU's for iSCSI Data > : In/Out segments. > : > I guess I'm worried that someone could issue padded > : odd-length write/read > : > data when it wasn't necessary. Example: When moving a 512 byte disk > : sector > : > an initiator/target could legally issue 512 1-byte DataSegmentLength > : > messages (each padded up to a 32-bit boundary). This isn't > : the sort of > : data > : > stream one would expect, but it's allowed in the draft. > : > > : > This also leads into whether fixed or minimum length data > : segments (for > : all > : > but the last) would be nice to include as part of the spec. > : It may result > : > in a simpler software/hardware design. > : > > : >
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