RAID Study Group Minutes 3/15/94

John Lohmeyer jlohmeye at ncr-mpd.FtCollinsCO.NCR.COM
Wed Mar 16 21:03:00 PST 1994

Minutes for RAID working group 03/15/94
Accredited Standards Committee
X3, Information Processing Systems
                                                      Doc. No.: X3T10/94-062R0
                                                          Date: March 15, 1994
                                                     Ref. Doc.:
                                                      Reply to: G. Penokie

To:         Membership of X3T10

From:       George Penokie and Ralph Weber

Subject:    Minutes of RAID Study Group Meeting
            March 15, 1994


 1.    Opening Remarks
 2.    Attendance and Membership
 3.    Approval of Agenda
 4.    Report on last RAID Working Group
 5.    Dual-Controller Issues
 6.    SCSI Disk Array Model (94-040r2)
 7.    SCSI-3 Addressing (94-031r2)
 8.    SDA Commands and Mode Pages (94-042r2)
 9.    SDA States and Types (94-041r2)
 10.   Error Handling for SCSI Controllers (94-024r2)
 11.   Action Items
 12.   Meeting Schedule
 13.   Adjournment

                               Results of Meeting

1.    Opening Remarks

George Penokie the RAID Study Group Chair, called the meeting to order at 9:08
am, Tuesday, 15 March 1994.  He thanked Qlogic for hosting the meeting.

As is customary, the people attending introduced themselves.  A copy of the
attendance list was circulated for attendance and corrections.

It was stated that the meeting had been authorized by X3T10 and would be
conducted under the X3 rules.  Ad hoc meetings take no final actions, but
prepare recommendations for approval by the X3T10 task group.  The voting
rules for the meeting are those of the parent committee, X3T10.  These rules
are:  one vote per company; and any participating company member may vote.

The minutes of this meeting will be posted to the SCSI BBS and the SCSI
Reflector and will be included in the next committee mailing.

George stated that this is the 17th meeting of the RAID study group and the
4th joint RAID Advisory Board/RAID study group meeting.  The purpose of the
group is to deal with interface issues related to using RAIDs.  The study
group will assess the issues and then formulate a strategy for dealing with

2.    Attendance and Membership

Attendance at working group meetings does not count toward minimum attendance
requirements for X3T10 membership.  Working group meetings are open to any
person or company to attend and to express their opinion on the subjects being

The following people attended the meeting:

                      RAID Study Group Meeting Attendees

                                                      Phone Number -or-
         Name          S       Organization         Electronic Mail Address
---------------------- - ------------------------- -------------------------
Mr. Randy Hall           Array Technology          303-938-6035
Mr. Thanh Pham           AST Research              714-727-6884
Mr. Charles Binford    A AT&T/GIS                  316-636-8566
Mr. M.W. Jibbe         A AT&T/GIS                  316-636-8810
Mr. Jeff Brown           Clariion-DG               508-898-5006
Mr. Ed Haske             CMD Technology            714-454-0800
Mr. Allan Cole           CORE International        407-997-6044 x505
Mr. Bill Dallas        A Digital Equipment Corp.   dallas at
Mr. Ralph Weber        A Digital Equipment Corp.   weber at
Mr. Mitch Rosich         EMC Corp.                 rosich at
Mr. Howard Grill         Formation                 609-234-5020
Mr. Bill Hutchison       Hewlett Packard Co.       hutch at
Mr. Andrew Hill          HI-Data                   617-937-6770
Mr. Paul Boulay          Hitachi Computer Products 408-986-9770
Mr. Ken Cummings       A IBM Corp.                 602-799-2182
Mr. Giles Frazier      A IBM Corp.                 512-838-1802
Mr. George Penokie     P IBM Corp.                 gop at
Mr. Kevin Pokorney       Intellistor/Fujitsu CPA   303-682-6649
Mr. Dave Fellinger       Mega Drive Systems        310-247-0006
Mr. Dick McCormick       Peer Protocols            714-476-1016
Mr. Herb Silverman       Peer Protocols            714-476-1016
Mr. Tony Fung            Storage Concepts          714-852-8511
Mr. Frank Ruthofford     Storage Concepts          714-852-8511
Mr. Atul Talati          Storage Concepts          714-852-8511
Mr. Robert N. Snively  P Sun Microsystems, Inc     bob.snively at
Mr. Joe Molina           Technology Forums         507-931-0967
Mr. Gary Watson          Trimm Industries          trimm at
Mr. Peter Dougherty      Unisys                    714-380-6270

Mr. Duck               D Hyatt pool
Mrs. Duck              D Hyatt pool

28  people present
2   ducks present

 Status Key:  P   -  Principal    ** X3T10 status still being defined
              A   -  Alternate
              O   -  Observer
              L   -  Liaison
              S,V -  Visitor
              D   -  Duck

3.    Approval of Agenda

The agenda developed at the meeting was approved.

4.    Report on last RAID Working Group

Last RAID Working Group was held in Austin, TX.  Several members of the RAID
Advisory Board were present.  George stated his intention that the minutes of
the Austin meeting be published on the SCSI Reflector.  Questions were raised
about whether that actually occurred.  George promised to review his minutes
publication practices.

5.    Dual-Controller Issues

George noted that the C-LUI concept may resolve most or all of the dual-
controller issues raised at previous meetings.  The C-LUI concept is discussed
in the new SCSI-3 Disk Array Model document (see below).  George reported that
Giles Frazier (IBM, Austin) and Doug Hagerman (Digital Equipment Corp.) both
have reviewed the SCSI-3 Disk Array Model from the perspective of dual con-
troller issues.  Giles has some small additions that should be added.  Doug
believes that C-LUIs cover all his concerns.  George is waiting for the dust
to settle.

Giles and George discussed this issues that Giles has raised.  The issues
revolve around the master/slave aspects of dual controller implementations.
How does a master exchange its ownership control with a slave?  What commands
are used?  How do addressing issues (LUN 0) get managed?

At this point, the discussion turned to a picture of a specific single
controller configuration.  The various P-LUI and C-LUI components were
identified, described (as to purpose), and named.  Then, the single controller
configuration was mirrored into a dual controller configuration.  A result of
this was broadening George's experience in dual controller configurations.

By the end of the discussion, George was convinced that most of the dual
controller issues are addressed by the current C-LUI concepts.  However,
George felt that additional descriptive text is necessary in the Disk Array
Model to clarify C-LUI application to dual controller configurations.

6.    SCSI Disk Array Model (94-040r2)

George presented a revised version of the SCSI-3 Disk Array Model

The major new concept in the revision of the SCSI-3 Disk Array Model is C-LUI.
A C-LUI is a Component Logical Unit Identifier.  A C-LUI represents an entity
that is not identifiable as a SCSI-3 Device Type.  To properly contrast with
this, the definition of P-LUI has been changed to make P-LUI represent an
entity that is identifiable as a SCSI-3 Device Type.

George walked through the Model discussing the specific effects of the C-LUI
addition.  At several points, corrections were noted to improve the details of
C-LUI definition and usage.

George noted a long-standing convention that he and Doug Hagerman have
discussed.  The Model describes redundancy groups as being attached to spares.
Doug prefers attaching spares to redundancy groups.  Recently, George realized
the conceptual benefits of using Doug's attachment model.  However, George
believes that the benefits of long-term consistence in the Model outweigh the
conceptual simplification provided by reversing what is attached to what.

Questions were raised regarding relationships when A is attached to B and B is
attached to C.  Can A be used as a path to gain information about C?  C-LUIs
complicate this problem, because C-LUIs can be attached to other C-LUIs.
Using C-LUIs as a mechanism for describing dual controller configurations also
may complicate this issue.  George was not certain that a problem really
exists.  George promised to work on the issue when/if its status becomes

As discussion progressed, the possible need for a new service was uncovered.
The new service would be directed to a P-LUI.  The service could be named
"Report P-LUI Attachments".  The service would ask the P-LUI to report
everything that is attached to it.  Upon further reflection, an equivalent
need was discovered for C-LUIs.  George agreed to add the service to the next
revision of the Model.

Questions were raised about what parts of the standard will be optional and
mandatory.  George felt that exact definition of optional and mandatory should
be left as one of the last steps in the standardization process.  If pressed
to guess, George felt that all the commands and services would be optional.
The addressing and states definitions might be mandatory.

George presented a list of possible C-LUI devices (things).  The list was
extracted from a private communication that George received from Doug
Hagerman.  George encouraged those attending to send him their lists.

7.    SCSI-3 Addressing (94-031r2) Penokie

George presented a revised version of the SCSI-3 Logical Unit Addressing
proposal (X3T10/94-031r2).  Concerns were raised about the relationship of
this P-LUI addressing scheme and the vendor-specific schemes already in use.
George noted that the existing vendor-specific schemes will be valid forever,
but he assumes that vendors will gradually convert to the standard
(generalized) scheme.

Other concerns were raised about the reduction of addressable volume set LUNs
|from 64 to 32.  George noted that the reduction has value, in the form of the
ability to address V-LUIs and P-LUIs without doing address remaps.

The level of change in 94-031r2 is very small.  George declared the document
stable.  He said that it will be presented to the X3T10 Plenary for approval
as soon as the SCC project proposal is approved by X3.

8.    SDA Commands and Mode Pages (94-042r2)

George presented a revision to the document defining the new commands and mode
pages needed to implement SCSI disk arrays (X3T10/94-042r2).  The major source
of changes was the addition of the C-LUI concept.

9.    SDA States and Types (94-041r2) Penokie

George presented the latest revision of the document defining states of an SDA
and the types of devices needed within Disk Arrays (X3T10/94-041r2).  There
was some discussion of the "base address" wording as opposed to the  "P-LUI 0"
wording.  In fairly short order, George was convinced to adopt the "base
address" terminology.

George noted several changes resulting from the new C-LUI concept.  The entire
list of C-LUI states is new.  George solicited proposals for C-LUI states in
addition to those that he has listed.

10.   Error Handling for SCSI Controllers (94-024r2) Hagerman (Weber)

Substituting for Doug Hagerman, Ralph Weber presented the latest draft of the
Error Handling for SCSI Controllers document (X3T10/94-024r2).  The document
was new to most people present.  Ralph describe how the lists of new ASC/ASCQs
on pages 7 through 9 were taken from the vendor-specific ASC/ASCQs of several
products that Digital markets.  Ralph also noted the addition of a Disk Array
device type column for the existing ASC/ASCQs.

George said that he wants to scan the lists for duplicates.  George described
the normal policy for defining new ASC/ASCQs, which includes a duplicates
check (made by George).  No one else had scanned the list for codes of
interest to them.  Some real-time scanning occurred during the meeting.

Some people present requested definition of some ASC/ASCQs that represent
x-LUI states (particularly failure-mode states).  George said that he will
consider that idea.

It was noted that Jerry Fredin (AT&T/GIS) has a list of ASC/ASCQs based on
contributions from manufacturers at the time the RAB was formed.  Although the
list is somewhat moldy now, it still is deemed to be a valuable reference.
Ralph was asked to have Doug contact Jerry.

11.   Action Items

  a) Penokie    Revise the SCSI Disk Array Model (94-040) document based on
                input received and toward making it cover dual controller
  b) Penokie    Revise the SDA States and Types (94-041) document.
  c) Penokie    Revise the SDA Commands and Mode Pages (94-042) document to
                account for the "report attachments" service.
  d) Hagerman   Contact Jerry Fredin (AT&T/GIS) for original manufacture
                inputs regarding vendor-specific ASC/ASCQ definitions for
  e) Hagerman   Revise the Error Handling for SCSI Controllers (94-024)

12.   Meeting Schedule

The next meeting of the RAID Study Group is planned for April 19, 1994 at
the Hyatt Regency in Bellevue, WA.  The meeting is expected to run from
9:00am-5:00pm.  This meeting will be a joint RAID Advisory Board Host
Interface Group and X3T10 RAID Study Group meeting.

13.   Adjournment

The meeting was adjourned at 3:11 pm. on Tuesday, 15 March, 1994.

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