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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: iSCSI : default iSCSI mode page settings - Consensus callBob, I think I agree with the direction of the note, but need to be sure we are on the same (mode) page:-) If you are saying the some values that effect an LU should be in LU specific Mode Pages, then fine in theory. I just need to understand which ones you are referring to. Since many of the Session parameters must be applied at the Transport, we need to know which iSCSI negotiated values you feel should be in the LU specific mode pages? Or did I miss understand you statements? . . . John L. Hufferd Senior Technical Staff Member (STSM) IBM/SSG San Jose Ca Main Office (408) 256-0403, Tie: 276-0403, eFax: (408) 904-4688 Home Office (408) 997-6136 Internet address: hufferd@us.ibm.com Robert Snively <rsnively@Brocade.COM>@ece.cmu.edu on 10/02/2001 08:36:18 AM Sent by: owner-ips@ece.cmu.edu To: ips@ece.cmu.edu cc: Subject: RE: iSCSI : default iSCSI mode page settings - Consensus call Folks, In an offline discussion, we have picked at a thread central to this fabric. That is basically the view that one has of the structure of targets. ------------------ Note sent out a day ago --------------- Traditional network environments talk from one big host memory to another big host memory. In the storage space, the memory in the target is actually distributed between whatever caching and preprocessing space the target platform may have and the space held by each logical unit. In some cases (RAIDs) the distribution is heavily in favor of the target platform cache. In others (tapes), individual logical units may have 100s of Megabytes of buffering which are not available to other logical units. If you have mixed types of logical units or if you have the memory distributed unevenly among the logical units, different values are normal among different LUs. Different sessions to the same LU may also have different properties. In particular, the LU may give away resources freely for the first few sessions, but more sparingly for subsequent sessions. Alternatively, the LU may share the resources dynamically, providing UNIT ATTENTION indications if it must change the values. The iSCSI target is merely a handy portal to the logical units and device servers, which really run the show. While many targets are simplified, sharing parameters across LUs and sessions, there is no requirement for that. Sophisticated devices may have individual parameters for each LU and session. iSCSI is trying hard to ignore the differences between storage and networking devices, but the differences are justified and genuine. ---------------- Some of the questions that triggered the note ----- > Are you saying that these parameters need to be able to have different > values for each LU among several LUs of single target in a single > session? > > Also would different sessions to the same LU all need to use the same > value? --------------- And a succinct summary of the thoughts --------------- If I understand correctly, in your view, such parameter negotiations should be per initiator and per LU. Parameters which are unique per logical unit can be set (or "negotiated") *only* via mode pages. Whether or not changing the value for one logical unit changes it for others would be target end implementer's choice, subject to appropriate parameter change notifications to the initiator(s). The values negotiated during login would be per initiator and per target default/initial values to be used when per LU mode pages have not been subsequently modified by this initiator. I am not reading that you think these values should not be settable at the per session level. Only that you believe there is a real need to be able to change them at the per LU level so that the per session values can be over-ridden for specific LUs. Changing the value for one LU via the mode pages would not have to change it for other LUs in this session nor for other sessions to this LU. Is that about right? --------- My answer would be yes -------------------------------------
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