FC_Tape Minutes Oct 7, 1998 Ft.Lauderdale
STEWART_R_WYATT at HP-Boise-om2.om.hp.com
STEWART_R_WYATT at HP-Boise-om2.om.hp.com
Wed Oct 14 07:07:29 PDT 1998
* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
* STEWART_R_WYATT at HP-Boise-om2.om.hp.com
Fibre Channel Tape Profile Meeting T11/98-523v0.pdf
Fort Lauderdale, Florida, October 7, 1998
1. Introductions: Group
Facilitator Dale LaFollette, StorageTek, called the meeting to order
shortly after 3 PM. He welcomed the participants and had everyone
2. Approval of Agenda: T11/98-487v0 Group.
The group approved the agenda without any change.
3. Approval of 9/15 Minutes: T11/98-473v0 Stewart Wyatt, HP.
The group approved the minutes without change.
4. Old Action Items: Stewart Wyatt
#1 Public/private addressing - Jim Coomes: On today's agenda
#2 ABTS proposal, updated, numbered and posted - Dave Peterson: Not
completed but on today's agenda.
#3 Review SMC SCSI commands and parameters for inclusion in the
profile - Dale Lafollette: Completed
#3 Update the Profile by September 24 - Dave Peterson: Completed
#4 Post a request for letter ballot on September 24 - Dale LaFollette:
5. Public/Private Addressing Continued: Jim Coomes, Seagate.
Jim found a lot of issues regarding when a public device may have to
accept the "0000" alias address instead of the "DDAA" address
particularly with regards to the discovery process. He started to put
together a table detailing when the 0000 address is required. Then he
concluded that to keep things simple he would propose having public
devices always respond to the 0000 alias.
A long discussion followed. Jeff Stai, Brocade, pointed out that Fibre
Channel requires each alias address to have a separate node name. The
need for this requirement was extensively debated. Charles Binford,
LSI Logic, said that this change would cause problems with existing
silicon. Jim noted that Seagate's earlier silicon will not support
this behavior but later silicon would. Bill Martin, Gadzook, was
concerned that responding to an ADISC addressed to the private device
with the public address would violate the rules. Pak Seto, Quantum,
suggested allowing only unsolicited frames to use 0000 and require all
others to use the DDAA address.
Then the discussion expanded to the FAN ELS. Since many of the
participants were not familiar with FAN some tutorial discussion was
solicited. The fabric sends out a FAN frame after a log
re-initialization. This allows each logged in device to check its Node
Name/Port Name/Native address against the value previously logged in
to the fabric. The devices are then able to validate themselves. If
the device finds the address has changed it does a logout. The
question was raised was raised as to whether FAN replaces the
discovery process on the local loop. The answer was that it does for
the public loop devices. Another discussion followed about possible
bugs in the FAN implementation. Matthew Wakeley, HP, was certain that
there a bug was introduced in allowing FAN to replace ADISC. Matthew
referred to the FLA clause 5.6.j.
After all of the discussion the group tried to come to a conclusion.
Jeff Stai thought the answer should be included in the FC-FS document.
Various proposals were submitted and discussed. Jim Coomes didn't want
to "play policeman" for initiators and so wanted the proposal worded
so as to allow flexibility for targets. The final proposal was to
require public devices to accept PLOGI, ABTS and LOGO frames with
either the DDAA address or the 0000 alias, but the device can (but
does not have to) discard all others frames received that are
addressed to the alias.
It was suggested that ACK and P_RJT be included but the group was not
able to document a need for them. Some additional discussion followed
about whether an ACK should include the 0000 alias or the DDAA address
in the S_ID field. Dal Allan, ENDL, said that FC-PH was very clear
that ACKS are created by reversing the S_ID and D_ID fields in the
received frame. The ACK then does not provide an opportunity for a
public device to return its correct address if it receives a frame to
the 0000 alias.
6. ABTS Enhancement Continued: Dave Peterson, StorageTek.
No application was found for the enhancements other than the
sequence/exchange bit in the parameter field. An uncompleted action
item was for Dave Peterson to update the ABTS proposal, assign a
document number and post it for review. Since it is documented in the
tape profile (in clause 9.5.4) which is shortly going for public
review, it was decided to cancel this action and rely on the profile
7. FCP_DL: Dale LaFollette
Dale posted an overhead with "7.4.2 FCP_RESID" text from the FCP
noting that when there is an FCP_RESID_OVER there is ambiguity in the
text as to the resulting action of the device. He presented a proposal
on an overhead hoping to minimize the ambiguity.
The original text (which was from the previous "Rev A" version of the
profile read, "FCP_DL in the FCP_CMND payload should always be equal
to the number of bytes expected to be transferred for the command."
Dale proposed changing the text to read, "FCP_DL in the FCP_CMND
payload shall always be equal to the number of bytes of the transfer
length in the CDB."
A heated discussion followed. Ed Gardner, Ophidian Designs, felt that
initiators would be forced to provide information unavailable to them.
Bob Snively, SUN, agreed with the goal of getting the tapes to behave
To sort out the discussion, Dale, provided an example on an overhead.
Imagine a tape with four fixed blocks of 100 bytes each. Three
different commands were considered. The first example was the most
interesting. A read command arrives where the CDB reads 4 blocks and
the FCP_DL has a value of 300 bytes. While the CDB requests a transfer
of 400 bytes, the FCP_DL restricts the transfer to 300. Dale asked
where the tape should be positioned after completing the command - at
the end of the third or the fourth block. Dal Allan thought the answer
was completely obvious. The CDB instructs the drive to read four
blocks. That is the overriding command. The FCP_DL restricts the data
transferred to the first three blocks. The result is that the tape
transfers the first three blocks but is positioned after the fourth
Editor Dave Peterson pointed out that he had already modified the
draft from what Dale had posted. Dave had already made some of the
same changes that Dale proposed. His changes included specific
instructions about how the FCP_DL byte length was calculated. Dave's
draft was accepted after changing "expected to be transferred" to
"requested in the CBD".
8. FC-TAPE Draft Review: T11/98-124vB Dave Peterson
Matthew Wakeley objected to the having the profile restrict SCSI
commands. He preferred the approach used in the PLDA which required
certain commands and allowed all others. He felt that the restrictions
violated the goal of allowing existing SCSI implementations to be
easily converted to Fibre Channel.
Dale LaFollette argued that the goal of interoperability requires
specifying a minimum set of commands. Bob Snively said that he
currently has to have a unique driver for every different tape drive
and wants to have this profile help limit the variations towards
enabling a common driver. Brian Smith, Crossroads noted that using
hierarchical drivers is an approach to reduce the magnitude of the
problem Bob described. Dal Allan noted that Bob Snively had raised the
scope of the profile with this approach which had been previously
agreed to by this group. This argument has been rehashed before here
and in previous profile discussions. Jim McGrath, Quantum, ridiculed
the use of the term prohibited which varies from the normal English
use of the term. (Jim was not in attendance last month when the choice
of terms was debated at length and so his criticism was not acted
After an extended discussion the issue was dropped for letter ballot
The next issue raised was allowing the port name to be equal to the
node name. Some heated discussion followed as to whether this is
prohibited in FC-PH. Bob Snively was adamant that it was prohibited
while Charles Binford, LSI Logic, Dave Baldwin, Emulex, and Brian
Smith, Crossroads felt that it was allowable and have implementations
that are doing this.
Dal Allan responded that it was prohibited in FC-PH. Bob noted the
prohibition is in FC-PH clause 3.1.99. Charles reviewed the text and
still felt there interpretation was valid. Dal Allan believed it was
prohibited but that the PLDA had allowed it in a footnote. The
footnote is in clause 5.1 note 4. Dal said the footnote was inserted
only to cover existing implementations NOT to justify new designs. He
noted that this has issue has been repeatedly debated, most recently
in Hawaii, and the decision to not allow this behavior has been
repeatedly upheld, however ignored by those who wish to continue this
The facilitator called a straw poll. The results were that 10
participants were opposed to allowing the node name to be equal to the
port name and 5 were in favor of allowing it. The conclusion then was
to reject the comment and make no mention of the subject in the
profile, deferring the issue to FC-PH and to not include the footnote
from the PLDA.
The next issue was noting that the text in clause "9.4, FCP Error
Recovery (Target Class 2)" was incorrect, having been obsoleted by the
new ABTS model. The decision was to eliminate the second and third
sentences of the second paragraph.
Next Dave Peterson asked the group if RRQ (see clause 9.5.7) should be
different for the two flavor of ABTS (abort sequence and abort
exchange). No one had an opinion so Dave said he would look into it
Dave had added a row to the bottom of "Table 25 - Clearing Effects of
SCSI Initiator Actions" on page 58 of the rev B version of the profile
to document the clearing effects of persistent reservations. Bob
Snively noted that tape drives are not expected to keep persistent
reservations across power cycles like disk drives are. This behavior
is controlled by the APTPL bit and is mentioned in footnote 11 of the
table. Bob said that tapes typically do not have access to nonvolatile
memory like disk drives do making persistent reservations more
difficult for tape drives to implement. However, he doesn't anticipate
a need to power cycle tape drives like disk drives do when being hot
plugged making this feature less necessary.
A comment was made that a SCSI reset and a power cycle are supposed to
produce the same results. The variation in the behavior of persistent
reservation violated that rule. That comment was acknowledged but it
was noted that the SCSI committee had approved this exception.
Matthew Wakeley had submitted some comments which were reviewed by the
In "Table 6 - NL_Port and N_Port Common Service Parameters (PLOGI)",
of the current draft of the profile Dynamic Half Duplex - DHD is set
to 0. Matthew wanted it removed from the table. There was some
opposition to this request but Dal Allan noted that the group had
previously agreed to remove from the profile parameters negotiated at
login. Dal felt that port characteristic don't belong in the profile.
He thought that this item had been overlooked by the editor and should
have been removed. The editor, Dave Peterson, preferred to leave it in
the table and mark it with an "X". This way it wouldn't look like the
issue had been overlooked.
Matthew noted that the SEQ_CNT field in Table 6 should be an "X"
instead of a "1" to be consistent with other parts of text. This
change was agreed to.
Matthew noted that "Tables 8 and 9 - Class 2 Service Parameters (PLOGI
and FLOGI)" have a `1" in the Class validity row. This requires the
drive to support Class 2 which was not the intention of the profile.
The group concluded to add to the introductory text a statement that
these tables only applied to devices that choose to support Class 2.
Matthew also noted that note 1 in both of these tables is unnecessary
because the RX_ID is returned in the ACK and is known to the sequence
initiator. The group agreed to have the note removed. The group agreed
that in "Table 10 and 11 - Class 3 Service Parameters (PLOGI and
FLOGI)" should remain unchanged with regard to the Class validity bit
as Class 3 support is required by the profile.
Matthew had a number of comments about clause "5.13 Exchange and
Sequence Management". The text in this clause was largely copied from
the PLDA. The group agreed to have clauses 5.13.1 to 5.13.4 removed
and include a reference to the original sources to avoid duplicating
material in the profile. Paula Zoller, Exabyte, was concerned about
having to reference multiple documents to understand the intent of the
profile. Some comments were made about not wanting to include tutorial
information in the profile and suggestions to read Bob Kembel's
arbitrated loop book and/or hiring a consultant.
Matthew wanted to modify the note in "6.2 Alternate Login_BB_Credit
management" which was approved.
Matthew had several comments about clause "7 Timers on Public and
Private Loop". This portion of the text was largely lifted from the
disk profiles. Clause "7.4 Error_Detect Timeout (E_D_TOV)" item "c)"
is in error. The group agreed to remove the item from the profile.
Item "d)" is a minimum not a maximum and applies to sequence
initiator. This correction was accepted. Matthew wanted the
LIS_HOLD_TIME parameter in "Table 17 Timer Summary" removed. He noted
that this parameter is from the PLDA and is not included anywhere
else. The group agreed to have it removed.
Matthew had noted a very serious problem with the timers. He observed
that if write data is lost, the timers as defined will cause the
target to log out the initiator (RR_TOV = 2 sec) before the initiator
will try error recovery (FCP_TOV = 3 sec). The group decided to
redefine RR_TOV to be 2*FCP_TOV + R_A_TOV (SEQ_QUAL).
Matthew had comments on several of the figures in "Annex B Error
Detection and Recovery Diagrams". Most of his comments related to
Class 2 cases where the ACK was lost but the sequence initiator could
infer that the original frame arrived by receiving subsequent frames.
In Figure 11 an ACK is lost for a transfer ready. The write data would
arrive before the E_D_TOV timer expires and most likely the exchange
would have completed and status sent as well! Matthew thought it was
unnecessary to complete the ABTS procedure described in the figure.
Dave agreed to add a note to the figure. Similar cases occur with
missing ACKs from read and write commands where implicit confirmation
is provided by the arrival of data or a transfer ready.
Some discussion followed about what value Class 2 features were
providing to the profile. The summary of the discussion was that class
2 provides a means of short-circuiting the FCP_TOV timer, enabling the
device to discover the error sooner. (Editor's note - other benefits
to Class 2 have been presented in previous meetings.)
Matthew had a comment about the text associated with Figure 15. The
text stated that the during the error recovery from lost write data
frames that the target "may or may not" hold sequence initiative.
Matthew stated that the Fibre Channel specification states that the
target will not have sequence initiative after a sequence error.
Matthew was concerned about "Figure 20 SRR or SRR Response lost". This
figure combines two error cases. Losing the SRR and losing the ACC for
the SRR. Matthew felt they should be separated. If SRR arrives and the
ACC is lost, arrival of data implies delivery. Matthew was concerned
about potential malfunctions if the second SRR is blindly sent.
Matthew also requested that two additional figures be added to cover
lost ACK for FCP_DATA for read and write cases.
After Matthew's list was finished, Dale LaFollette raised the question
of why half duplex operations was prohibited. Rather than continuing
the discussion Dale said he would raise the issue in a letter ballot.
Charles Binford was concerned that the complete loss of a read data
sequence in a multiple sequence exchange could be undetected. As it
was late he agreed to post his concerns to the reflector.
9. T11 New Business: Group
a. FC-TAPE for T11 Letter Ballot: Group
It was getting late in the evening. A even dozen participants remained
in the room. Dale LaFollette asked the survivors if we should proceed
with a request tomorrow to ask for a letter ballot for the profile
draft that included the changes made in this meeting. The group agreed
unanimously go to the letter ballot.
There was some discussion about how soon the editor could get the
profile updated. Dale proposed two weeks though Dave thought he could
get it done sooner. Bob Snively wanted the editor to include a
persistent reservation table (98/T10-164v1) added to the document. He
suggested several sources that the editor could get it from and
offered to send a copy email if needed.
10. T10 New Business: Group
11. Review New Action Items: Stewart Wyatt
#1 Jim Coomes will update the public/private address proposal next
week for inclusion in the profile.
#2 Stewart Wyatt to get a resolution on HP SCSI command comments.
#3 Dave Peterson to get a copy of persistent resolution table for the
#4 Charles Binford to write up his concern about loss of a read data
sequence and post to reflector.
12. Adjournment: Group
The meeting was adjourned around 8:30 PM.
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