99-231r0 - EXTENDED COPY and Abort Task Management Functions

Ralph Weber ralphoweber at CompuServe.COM
Sat Aug 21 06:11:58 PDT 1999


* From the T10 Reflector (t10 at t10.org), posted by:
* Ralph Weber <ralphoweber at compuserve.com>
*
A proposal for consideration at the September meetings has
been placed on the T10 FTP site as:

< ftp://ftp.t10.org/t10/document.99/99-231r0.pdf >

The text of the proposal is included below.  However, the PDF
contains text formatting that cannot be represented in ASCII plain
text.  Please refer to the PDF if the information below catches your
interest.

Doc:  T10/99-231r0
Date: 18 August 1999
To:   T10 Technical Committee
From: Ralph Weber, LSI Logic Alternate Member of T10
Subj: EXTENDED COPY and Abort Task Management Functions

The ABORT TASK, ABORT TASK SET, and CLEAR TASK SET task management
functions may cause an EXTENDED COPY command to be terminated
prematurely.  When this occurs as a result of a persistent
reservations PREEMPT AND ABORT service action it is critical that the
copy manager cease all data transfers as part of completing the ABORT
TASK SET operation described in list entry b) in 5.3.2.5.3 (SPC-2 rev
11).

Two alternatives are proposed for instantiating this requirement in
SPC-2.  Two alternatives are necessary because task management
functions have less than perfectly defined completion notification
requirements, and the completion notification of the ABORT TASK SET
task management function is a key concept in one of the alternatives.

Alternative I

Since initiators using the ABORT TASK SET, et. al. task management
functions to prematurely terminate an EXTENDED COPY command probably
desire the same behavior as required by persistent reservations,
alternative I proposes to state the requirement as a requirement on
the copy manager for task management function support.  This would be
accomplished by adding a new clause to the EXTENDED COPY command
definition.

Pros

This alternative places the requirement text in the definition of the
EXTENDED COPY command, which is where developers of copy manager
functions are most likely to look for special requirements for their
software.

Cons

The mechanism by which an ABORT TASK SET task management function
indicates its completion had a weak definition, especially for some
SCSI protocols.  Thus, the statement '… before allowing the device
server to complete the task management function' is more open to
interpretation than might be desirable.

Specific Proposal

Add the following as clause 7.4.3 and renumber subsequent clauses as
necessary.

    7.4.3  Abort task management functions

    When a device server processes an ABORT TASK, ABORT TASK SET, or
    CLEAR TASK SET task management function that terminates an
    EXTENDED COPY command, the copy manager shall ensure that all
    commands it has issued pursuant to the EXENDED COPY command have
    been terminated and are no longer transferring data before
    allowing the device server to complete the task management
    function.  This requirement shall also apply to the processing
    the PREEMPT AND ABORT service action on the PERSISTENT RESERVE
    OUT command as described in 5.3.2.5.3.

Alternative II

State the requirement directly in the 5.3.2.5.3 description of the
PREEMPT AND ABORT service action.

Pros

This alternative leaves no confusion as to the requirements for the
PREEMPT AND ABORT service action.

Cons

The defined behavior for the ABORT TASK SET, et. al. task management
functions is ambiguous, although no worse so than for the COPY
command today.  Developers focused on the definition of the EXTENDED
COPY command may miss the requirement.

Specific Proposal

Modify list b) in clause 5.3.2.5.3 to read as follows (new text
underlined in the PDF):

    b)  Every task from all preempted initiators shall be terminated
    as if an ABORT TASK SET task management function had been
    performed by each of the preempted initiators. If a terminated
    task is a COPY or EXTENDED COPY command, all commands and data
    transfers generated by the command shall be terminated before the
    ABORT TASK SET task management function is considered completed.
    After the ABORT TASK SET function has completed, all new tasks
    are subject to the persistent reservation restrictions
    established by the preempting initiator;




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