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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: aborting an out of sequence cmdSNJulian, I understand that nothing in the current draft prevents usage of connection allegiance for an abort task to flush the stale PDUs of a command. However, as a target implementor, if such a guaranteed mechanism is not mandated to flush stale PDUs of a command, targets will need to build safeguards against possible stale PDUs from a command. Any such scheme would cause targets to retire resources until a safe period (based on a best guess !) has elapsed. The targets CANNOT depend on initiators deploying this scheme in the absence of the spec mandating this and do not have a guarantee that stale PDUs will not arrive after the Abort Task has cleaned up the command at the target end. Keeping in mind the above, I am asking that iSCSI mandate that the Abort Task be sent on the same connection as the SCSI command being aborted. In addition, [and this has been asked earlier], the iSCSI draft lacks a section on I/O timeout handling under the error recovery section. Some description must be provided on the actions an initiator should take on an I/O timeout. (or timeout of other iSCSI PDUs). For instance, should non-SCSI PDUs be timed ? (login, text, etc). If so, what is their timeout values. What actions should an initiator take if they time out. How is the task tag for that non-SCSI PDU cleaned up, ensuring no stale PDUs are going to arrive for that task tag. iSCSI Error Recovery descriptions MUST address task timeout handling. - Santosh julian_satran@il.ibm.com wrote: > > First the current draft does not stop you from doing what you want - it > just does not mandate it. > Second with CmdSN now you have a better chance - before handing the command > over to SCSI task management > mark all the relevant commands in the iSCSI queue as non-deliverable to a > LUN or all LUNs or keep a stack of barriers for active aborts (I assume > that this is a reasonably low number) to the same effect. > > Julo > > Santosh Rao <santoshr@cup.hp.com> on 18/04/2001 01:10:17 > > Please respond to Santosh Rao <santoshr@cup.hp.com> > > To: Sandeep Joshi <sandeepj@research.bell-labs.com> > cc: ips@ece.cmu.edu > Subject: Re: aborting an out of sequence cmdSN > > I'd think option 1 is the simplest (with the caveat that the task mgmt > PDU referred to is the Abort Task.) and only impacts the affected > command/task. > > Pierre Labat and I have asked for this 4 months ago. (See : > http://ips.pdl.cs.cmu.edu/mail/msg02958.html). The concept of connection > allegiance should be extended to include the Abort Task. Also, > connection allegiance should apply to the task (which spans multiple > commands in the case of linked commands.), allowing for a deterministic > clean up of stale PDUs of the task through the use of Abort Task. > > - Santosh > > Sandeep Joshi wrote: > > > > > So our options for abort_task boil down to.. > > (1) use connection allegiance for TASK MGMT PDU. > > (2) reject all commands prior to cmdSN of TASK MGMT PDU. > > (3) cmdSN of original task is sent with TASK MGMT PDU and > > target at the iSCSI layer keeps state. > > (4) iSCSI initiator retains state for deleted tasks to ensure > > that R2T/Scsi Responses are appropriately handled. > - santoshr.vcf begin:vcard n:Rao;Santosh tel;work:408-447-3751 x-mozilla-html:FALSE org:Hewlett Packard, Cupertino.;SISL adr:;;19420, Homestead Road, M\S 43LN, ;Cupertino.;CA.;95014.;USA. version:2.1 email;internet:santoshr@cup.hp.com title:Software Design Engineer x-mozilla-cpt:;21088 fn:Santosh Rao end:vcard
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