Fw: FCP-2: Lost Write Data, Not Last Frame of Sequence, Unacknowledged classes.
hcurley at indra.com
Fri Jun 28 14:06:26 PDT 2002
* From the T10 Reflector (t10 at t10.org), posted by:
* "Hugh Curley" <hcurley at indra.com>
Dave, Santosh and other readers,
Sorry, I missed the response that was published.
----- Original Message -----
From: "Dave Peterson" <dap at cisco.com>
To: "Santosh Rao" <santoshr at cup.hp.com>; "T10 Reflector" <t10 at t10.org>
Sent: Wednesday, June 26, 2002 23:18
Subject: RE: FCP-2: Lost Write Data, Not Last Frame of Sequence,
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "Dave Peterson" <dap at cisco.com>
> Howdy Santosh,
> Comments below...dap
> > -----Original Message-----
> > From: owner-t10 at t10.org [mailto:owner-t10 at t10.org]On Behalf Of Santosh
> > Rao
> > Sent: Tuesday, June 25, 2002 7:18 PM
> > To: T10 Reflector
> > Subject: FCP-2: Lost Write Data, Not Last Frame of Sequence,
> > Unacknowledged classes.
> > * From the T10 Reflector (t10 at t10.org), posted by:
> > * Santosh Rao <santoshr at cup.hp.com>
> > *
> > Hello,
> > We have a question regarding Annexe C Figure C.15 of FCP-2 Rev 07a. This
> > figure depicts the FCP-2 SLER (sequence level error recovery) for the
> > case of a lost write data iu which is not the last frame in the sequence
> > for an un-acknowledged class.
> > The figure shows the recovery as :
> > "Wait REC_TOV. If FCP_DATA is returned, continue with the exchange.
> > Otherwise, perform error recovery".
> > Are the above statements referring to the actions to be taken by the
> > initiator or the target ? Since this is a write operation, it is not
> > clear how FCP_DATA could be returned to the initiator. (?)
> The statements refer to the actions to be taken by the initiator.
> But, I don't know how FCP_DATA could be returned for a write operation
> The note is not correct and should be removed. I think the intent was to
> specify the behavior for out-of-order class 3.
> > Since the last frame of the sequence is assumed to have made it to the
> > target (lost write data iu was not the last frame of sequence), the
> > target has the sequence initiative and can complete the exchange with a
> > FCP_RSP indicating a CHECK CONDITION status with appropriate sk/asc/ascq
> > (as per Section 9.4.1). In this case, is the initiator expected to look
> > for CHECK CONDITION command completions of certain sk/asc/ascq
> > combinations and initiate a SLER operation on seeing those ? What
> > specific sk/asc/ascq combinations should the initiator look for while
> > parsing command completions to initiate SLER ?
> > If this is not done, a write underrun condition as described above
> > cannot be recovered from, since SLER will not kick in and the
> > ULP/application will see the error.
> > Can someone clarify what is the error recovery actions taken by the
> > initiator and target in this situation ?
> For this case:
> The target may or may not have sequence initiative
> (i.e., seq=1, seq_cnt=1 may not be the last frame of the sequence).
> For in-order delivery the target should have detected a Sequence error.
> Per clause 12.3.5 Additional error recovery by target:
> For unacknowledged classes of service, the target shall not attempt
> for Sequence errors. The target
> shall depend on initiator time-outs for recovery.
> If SLER is enabled, the target should not return check condition.
> And we could use some words stating this in the doc...dap
> > Thanks,
> > Santosh Rao
> > --
> > The world is so fast that there are days when the person who says
> > it can't be done is interrupted by the person who is doing it.
> > ~ Anon
> > *
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