TASK SET FULL Definition(s) in FC-TAPE and SAM-2

[Bob Snively]

* From the T10 Reflector (t10 at symbios.com), posted by:
* Bob Snively <Bob.Snively at Ebay.Sun.COM>
*
Yep,

Sorry.

That does not change my recommendation that TASK SET FULL be mandatory
behavior for FC-TAPE compliant initiators.

Bob


> Bob,
> It is not illegal for a target to process two untagged commands from
> different initiators at the same time. It is illegal to request the target
> process two untagged commands from the same initiator at the same time.
> 
> Bye for now,
> George Penokie
> 
> Dept PPV  114-2 N212
> E-Mail:    gop at us.ibm.com
> Internal:  553-5208
> External: 507-253-5208   FAX: 507-253-2880
> 
> 
> 
> 
> Bob Snively <Bob.Snively at Ebay.Sun.COM> on 03/17/99 10:40:28 AM
> 
> Please respond to Bob Snively <Bob.Snively at Ebay.Sun.COM>
> 
> To:   dap at nsg0.network.com, t10 at Symbios.COM, fc at nsg0.network.com
> cc:    (bcc: George Penokie/Rochester/IBM)
> Subject:  Re: TASK SET FULL Definition(s) in FC-TAPE and SAM-2
> 
> 
> 
> 
> 
> * From the T10 Reflector (t10 at symbios.com), posted by:
> * Bob Snively <Bob.Snively at Ebay.Sun.COM>
> *
> 
> Realistically, after placing my answers in the section below, I believe
> that tagged queueing must be supported by FC-TAPE compliant initiators,
> since only such initiators will do anything intelligent with
> QUEUE FULL (TASK SET FULL).  Typically, their action is to retry
> infrequently and in addition to retry whenever a task is completed from
> that logical unit.
> 
> Then the "cleaner" TASK SET FULL behavior can replace the present
> proper SCSI behavior of "vendor specific" or "OVERLAPPED COMMANDS
> ATTEMPTED."
> 
> See my notes below.
> 
> > FC-TAPE currently states in clause 9.2 for TASK SET FULL:
> >
> > - TASK SET FULL (if Tagged Queuing is used or ULP resources are
> > unavailable)
> >
> > SAM-2r10 states in clause 5.2:
> >
> > TASK SET FULL. This status shall be implemented if the logical unit
> > supports the creation
> > of tagged tasks (see 4.9). This status shall be returned when the
> > logical unit receives a
> > command and does not have enough resources to enter the associated task
> > in the task set.
> >
> > SAM-2r10 states in clause 4.8:
> >
> > A Task Set is composed of zero or more Untagged Tasks or a combination
> > of zero or more
> > Tagged Tasks and zero or more Untagged Tasks.
> >
> > So it seems to me TASK SET FULL should be implemented regardless.
> >
> > Another issue: what is the proper SCSI Status to return if:
> >
> > a) the lun does not support tagged tasks, is processing a command
> > received from one Initiator (has no reservation active), has enough
> > resources to receive another command and enter it into the Task Set,
> > and receives another command from a different Initiator.
> >
> > My preference would be a BUSY.
> 
> The answer here is VENDOR SPECIFIC.  BUSY is correct if there are no
> resources and the device does not know how to juggle two tasks.  In
> an FC-AL device, this will be very unlikely, since juggling two or more
> exchanges is normal.  As a result, the proper behavior is probably
> to accept and execute the new command in its turn.  That is very
> bad behavior by a tape applications, which is why we have made
> reservations a requirement in tape drives.
> 
> 
> >
> > b) the lun does not support tagged tasks, is processing a command
> > received from one Initiator (has no reservation active), does not have
> > enough resources to receive another command and enter it into the
> > Task Set,  and receives another command from a different Initiator.
> >
> > I would expect a TASK SET FULL.
> 
> There is a CHECK CONDITION ASC/ASCQ assigned for this behavior:
> 
>      ASC/ASCQ 48/00  OVERLAPPED COMMANDS ATTEMPTED
> 
> The check condition is provided by either command and the other is
> automatically aborted.
> 
> 
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