Fw: TMF text with updates
"Mallikarjun C." <[email protected]>
| Newsgroups | gmane.ietf.ips |
|---|---|
| Message-ID | <[email protected]> |
Forgot to copy to the list. ----- Forwarded Message ---- From: Mallikarjun C. <[email protected]> To: Julian Satran <[email protected]> Sent: Thursday, December 28, 2006 12:09:16 PM Subject: Re: [Ips] TMF text with updates Julian, Thanks for the quick review. I agree with your point on the bullet (c) - it was a relic. I now fixed the text per your feedback. On your alternative proposal to send a TMF on every connection, I would need more details.... I do not see any issues with the third-party initiator sessions so far, with the current text we have. The TaskReporting key is a session-scoped key that the target tracks on a session-by-session basis. Mallikarjun ----- Original Message ---- From: Julian Satran <[email protected]> To: Mallikarjun C. <[email protected]> Cc: [email protected] Sent: Thursday, December 28, 2006 2:31:49 AM Subject: Re: [Ips] TMF text with updates Mallikarjun, I would consider the text: c. MUST leave all active "affected TTTs" (i.e. active TTTs associated with affected tasks) valid along with any buffer allocations for the TTTs intact. somewhat excessive as it relates too much to implementation. I would rather say: c. MUST leave all active "affected TTTs" (i.e. active TTTs associated with affected tasks) valid. and leave the buffer issue to the implementer (as I have stated already on this list). I also keep thinking (and mildly objecting to) that the whole fast abort is excesively complex. You could achive the same effect by issuing the TM command on every affected connection. The third party story is even more puzzling as in order to negotiate any of the nem TM modes the taget will have to ascertain that all other initiators support it. I fail to understand how would you handle downgrading the mode for those that don't. And if you don't downgrade why not state that fast-abort and target scoped queues don't go together and simplify the mechanics to a multiple issue TM. Thanks, Julo "Mallikarjun C." <[email protected]> 28/12/06 06:41 [email protected] cc Subject[Ips] TMF text with updates Attached is the latest text that incorporates David's proposed enhancement. Please review and comment. Note especially two things: new section 4.1.4 that summarizes generic implementation considerations for both "clarified" and "updated" semantics, the changed text in 4.1.2 that says "MAY wait for ....target transfer tags.....from third-party initiators" from the previous blanket MUST. Mallikarjun 4.1.2 Clarified multi-task abort semantics All iSCSI implementations MUST support the protocol behavior defined in this section as the default behavior. The execution of ABORT TASK SET, CLEAR TASK SET, LOGICAL UNIT RESET, TARGET WARM RESET, and TARGET COLD RESET TMF Requests consists of the following sequence of actions in the specified order on the specified party. The initiator iSCSI layer: a. MUST continue to respond to each TTT received for the affected tasks. b. Should receive any responses that the target may provide for some tasks among the affected tasks (may process them as usual because they are guaranteed to have chronologically originated prior to the TMF response). c. Should receive the TMF Response concluding all the tasks in the set of affected tasks. The target iSCSI layer: a. MUST wait for currently valid target transfer tags of the affected tasks from the issuing initiator to be responded to. MAY wait for responses on currently valid target transfer tags of the affected tasks from third-party initiators. b. MUST wait (concurrent with the wait in Step.a) for all commands of the affected tasks to be received based on the CmdSN ordering. SHOULD NOT wait for new commands on third-party affected sessions - only the instantiated tasks have to be considered for the purpose of determining the affected tasks. In the case of target-scoped requests (i.e. TARGET WARM RESET and TARGET COLD RESET), all the commands that are not yet received on the issuing session in the command stream however can be considered to have been received with no command waiting period - i.e. the entire CmdSN space up to the CmdSN of the task management function can be "plugged". c. MUST propagate the TMF request to and receive the response from the target SCSI layer. d. MUST address the Response Fence flag on the TMF Response on issuing session as defined in 3.3.2. e. MUST address the Response Fence flag on the first post-TMF Response on third-party sessions as defined in 3.3.2. If some tasks originate from non-iSCSI I_T_L nexuses then the means by which the target ensures that all affected tasks have returned their status to the initiator are defined by the specific non-iSCSI transport protocol(s). Implementation note: Technically, the TMF servicing is complete in Step.d. Data transfers corresponding to terminated tasks may however still be in progress on third-party iSCSI sessiosn even at the end of Step.e. TMF Response MUST NOT be sent by the target iSCSI layer before the end of Step.d, and MAY be sent at the end of Step.d despite these outstanding Data transfers until after Step.e. 4.1.3 Updated multi-task abort semantics Protocol behavior defined in this section MUST be implemented by all iSCSI implementations complying with this document. Protocol behavior defined in this section MUST be exhibited by iSCSI implementations on an iSCSI session when they negotiate the TaskReporting (section 9.1) key to “FastAbort” on that session. The execution of ABORT TASK SET, CLEAR TASK SET, LOGICAL UNIT RESET, TARGET WARM RESET, and TARGET COLD RESET TMF Requests consists of the following sequence of actions in the specified order on the specified party. The initiator iSCSI layer: a. MUST NOT send any more Data-Out PDUs for affected tasks on the issuing connection of the issuing iSCSI session once the TMF is sent to the target. b. Should receive any responses that the target may provide for some tasks among the affected tasks (may process them as usual because they are guaranteed to have chronologically originated prior to the TMF response). c. MUST respond to Async Message PDU with AsyncEvent=5 as defined in section 8.1. d. Should receive the TMF Response concluding all the tasks in the set of affected tasks. The target iSCSI layer: a. MUST wait for all commands of the affected tasks to be received based on the CmdSN ordering on the issuing session. SHOULD NOT wait for new commands on third-party affected sessions - only the instantiated tasks have to be considered for the purpose of determining the affected tasks. In the case of target-scoped requests (i.e. TARGET WARM RESET and TARGET COLD RESET), all the commands that are not yet received on the issuing session in the command stream however can be considered to have been received with no command waiting period - i.e. the entire CmdSN space up to the CmdSN of the task management function can be "plugged". b. MUST propagate the TMF request to and receive the response from the target SCSI layer. c. MUST leave all active "affected TTTs" (i.e. active TTTs associated with affected tasks) valid along with any buffer allocations for the TTTs intact. d. MUST generate an Asynchronous Message PDU with AsyncEvent=5 (section 8.1) on: i) each connection of each third-party session that at least one affected task is allegiant to, and ii) each connection except the issuing connection of the issuing session that has at least one allegiant affected task. If there are multiple affected LUs (say due to a target reset), then one Async Message PDU MUST be sent for each such LU on each connection that has at least one allegiant affected task. e. MUST address the Response Fence flag on the TMF Response on issuing session as defined in 3.3.2. f. MUST address the Response Fence flag on the first post-TMF Response on third-party sessions as defined in 3.3.2. If some tasks originate from non-iSCSI I_T_L nexuses then the means by which the target ensures that all affected tasks have returned their status to the initiator are defined by the specific non-iSCSI transport protocol(s). g. MUST free up the affected TTTs (and STags, if applicable) and the corresponding buffers once it receives the associated Nop-Out acknowledgement that the initiator generated in response to the Async Message. Implementation note: Technically, the TMF servicing is complete in Step.e. Data transfers corresponding to terminated tasks may however still be in progress even at the end of Step.f. TMF Response MUST NOT be sent by the target iSCSI layer before the end of Step.e, and MAY be sent at the end of Step.e despite these outstanding Data transfers until Step.g. Step.g specifies an event to free up any such resources that may have been reserved to support outstanding data transfers. 4.1.3.1 Clearing effects update Appendix F.1 of [RFC3720] specifies the clearing effects of target and LU resets on “Incomplete TTTs” as “Y”. This meant that a target warm reset or a target cold reset or an LU reset would clear the active TTTs upon completion. The TaskReporting=FastAbort (section 9.1) semantics defined by this section however do not guarantee that the active TTTs are cleared by the end of the reset operations. In fact, the new semantics are designed to allow clearing the TTTs in a “lazy” fashion after the TMF Response is delivered. Thus, when TaskReporting=FastAbort is operational on a session, the clearing effects of reset operations on “Incomplete TTTs” is “N”. 4.1.4 Implementation considerations Both in clarified semantics (section 4.1.2) and updated semantics (section 4.1.3), there may be outstanding data transfers even after the TMF completion is reported on the issuing session. In the case of iSCSI/iSER [iSER], these would be tagged data transfers for STags not owned by any active tasks. Whether or not real buffers support these data transfers is implementation-dependent. However, the data transfers logically MUST be silently discarded by the target iSCSI layer in all cases. A target MAY, on an implementation-defined internal timeout, also choose to drop the connections on which it did not receive the expected Data-out sequences (section 4.1.2) or Nop-Out acknowledgements (section 4.1.3) so as to reclaim the associated buffer, STag and TTT resources as appropriate. ----- Original Message ---- From: "[email protected]" <[email protected]> To: [email protected]; [email protected]; [email protected] Sent: Wednesday, December 20, 2006 2:33:43 PM Subject: RE: [Ips] Implementer's Guide - Task Management Issue > Let's try this line of reasoning - the target issues the Nop-Out, now when > can it free the resources? Answer: > - The Nop-In response comes back, OR > - The connection times out and is torn down. > Now, what if the Nop-Out is not issued - what does the target wait for to > free the resources? Answer: > - The transfers complete, OR > - The connection times out and is torn down. > Those look similar enough at the target (the worst case is the same - the > resources are tied up until an uncooperative initiator times out) that > I don't see the harm in allowing the early TMF return without the new > key. The clear distinction is that the first two bullets are different; > if the new key is not negotiated, the target has to wait for the transfers > to complete; the new key and the Nop-Out are necessary to walk away earlier > when the initiator involved is able to continue the transfers. That got slightly twisted - what it should have talked about was the target issuing the new Async Message and the Nop-Out response coming back. Thanks, --David ---------------------------------------------------- David L. Black, Senior Technologist EMC Corporation, 176 South St., Hopkinton, MA 01748 +1 (508) 293-7953 FAX: +1 (508) 293-7786 [email protected] Mobile: +1 (978) 394-7754 ---------------------------------------------------- __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ Ips mailing list [email protected] https://www1.ietf.org/mailman/listinfo/ips __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ Ips mailing list [email protected] https://www1.ietf.org/mailman/listinfo/ips