FC Reservations

Brian McKean bmckean at mylexboulder.com
Mon Mar 30 15:48:26 PST 1998


* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
* bmckean at mylexboulder.com (Brian McKean)
*
Thanks for the clarification Charles,

On the PLRI (question 1.3)
Your interpretation is what I'd like to implement.  I think I should clear
reservations and give a 06-2900 UA to all other initiators.

But there are two sentences in the the paragraph that seem to explicitly
state that I cannot clear reservations for other initiators.  Here is the
second paragraph under section 6.2.5 of FCP r12 in its entirety with the two
sentences enclosed in <<< >>>.


Immediately after the execution of a PRLI, both members of the image pair
shall have the same state as they would have after a hard reset or a power
on with respect to each other. No tasks, reservations or status except those
previously established between other image pairs sharing one of the process
associators shall be present in either SCSI device. The MODE SELECT
parameters will assume their default or saved states for that image pair.
<<< Tasks, reservations, status, and MODE SELECT parameters for other
initiators are not affected.>>> A Unit Attention condition (Sense Key = 6)
with an Additional Sense Code of Reset Occurred (ASC = 29, ASCQ = 00) shall
be presented upon the first attempt to communicate between the image pairs
using FCP when a new PRLI has been performed. <<<Target port shall not
generate a unit attention condition for initiators which are already logged
in.>>> Initiators shall indicate to their host systems that an image pair
has been reset and that any outstanding operations for the image pair have
been reset.




Binford, Charles wrote:

> * From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
> * "Binford, Charles" <charles.binford at symbios.com>
> *
> Brian, this question was asked last fall on the disk_attach reflector.
> At that time I asked Dave Peterson as the editor of PLDA-2 to add
> reservation into table 16.  Between then and now PLDA-2 as turned into
> FC-TAPE, so I'm not sure if the answer to this question has a document
> home or not.
>
> Anyway, my understanding of things gives the answers below.
>
> Charles Binford
> Symbios Inc.
>
>  ----------
> >From: bmckean at mylexboulder.com
> >To: SCSI Reflector; Fibre Channel Reflector
> >Subject: FC Reservations
> >Date: Monday, March 30, 1998 11:53AM
> >
> >
> >I'd like some help to understand when reservations (using
> >Reserve/Release, not persistent reservations) are cleared under FC-AL.
> >
> >1. Which loop operations cause ALL device reservations to be cleared
> and
> >which cause only reservations cleared for the initiator that performs
> >the operation?
> >
> >     FC-PLDA rev 2.1 table 16 lists when to clear "FCP SCSI Target
> >     Objects"  but does not list reservations.
> >     1.1 The easy ones for clear ALL would be:
> >          a.  Device power on or hard reset
> >          b. Target Reset task management function ( FCP_CNTL  Target
> >          Reset)
>
> agreed
>
> >
> >     1.2 What about LIP reset L_PORT ?
>
> If I'm the device being selectively reset, then yes, clear the
> reservations (treat as hard reset).  If someone else is being reset, or
> any other flavor of LIP, then no, don't clear the reservation.
>
> >
> >     1.2 What about PLOGI ?
>
> Yes, clear the reservation.  This includes explicit and implicit LOGO as
> well.  Note, that not "checking in" after a normal LIP can cause an
> implicit logout, thus clear a reservation.
>
> >
> >     1.3 What about PRLI ?
> >          FCP r12 section 6.2.5 New or repeated PRLI (second paragraph)
> >          mentions reservations:
>
> Yes, clear the reservation.
>
> >
> >               Immediately after the execution of a PRLI, both members
> >               of the
> >               image pair shall have the same state as they
> >               would have after a hard reset or a power on with respect
> >               to each other.
> >          and
> >
> >               Tasks, reservations, status, and MODE SELECT
> >               parameters for
> >               other initiators are not affected.
>
> I think you misread FCP.  Here is the exact text I think you are
> referring to:
> "Immediately after the execution of a PRLI, both members of the image
> pair shall have the same state as they
> would have after a hard reset or a power on with respect to each other.
> No tasks, reservations or status except
> those previously established between other image pairs sharing one of
> the process associators shall be present
> in either SCSI device."
>
> The confusing part is in the last sentence.  The clause "...except those
> previously established between other image pairs sharing of the process
> associators...." refers to those using process associators.  For all of
> us NOT using process associators I would change the last sentence to:
> "No tasks, reservations or status shall be present in either SCSI
> device."
>
> >
> >           This seems contradictory.  After hard reset or power on ALL
> >          reservations would be cleared.   How can the target behave as
> >          if power on occurred but still preserve reservations for
> other
> >          initiators?
> >
> >     Any others I didn't think of?
> >
> >
> >2. A separate question:   PLOGI in table 16 it says to restore mode
> >pages from saved pages only for port initiating action.  It shows for
> >all other SCSI initiators that mode pages are NOT restored from saved.
> >Does this imply that mode pages must be kept on a per initiator basis?
> >
> >
> >Thanks,
> >
> >Brian McKean
> >
> > --
> >
> >Brian McKean                             Voice: (303)381-4246
> >Mylex Corporation External Products      Fax:   (303)413-0464
> >4900 Pearl East Circle Suite 104         brianm at mylexboulder.com
> >Boulder, CO 80301-6108
> >http://www.mylex.com
> >
> >
> *
> * For T10 Reflector information, send a message with
> * 'info t10' (no quotes) in the message body to majordomo at symbios.com



--

Brian McKean                             Voice: (303)381-4246
Mylex Corporation External Products      Fax:   (303)413-0464
4900 Pearl East Circle Suite 104         brianm at mylexboulder.com
Boulder, CO 80301-6108
http://www.mylex.com


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