One last plea for correct behavior of mode select pages

Robert Snively rsnively at Brocade.COM
Tue Feb 13 10:09:39 PST 2001


* From the T10 Reflector (t10 at t10.org), posted by:
* Robert Snively <rsnively at brocade.com>
*
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Note my comments at the end, where I indicate my dissatisfaction with
the agreed-upon solution.  This is likely to come back and haunt us in
no uncertain terms.  Customers who demand this of their vendors should
be either educated or provided with an explicitly non-standard product.
The standard product should have a defined current value after a first
PRLI with shared mode pages equal to the saved or default values, as
specified by SCSI-2, SPC, and SPC-2.  Fudging this to be vendor specific
is a really bad idea.

I am soliciting correction of this at the FCP-2 meeting in March.  It is
installed as shown below for now.

Bob

 

2.3  X47821_Heading2_23_Consideration of mode pages, technical

CPQ-003: PDF 33, Page 19 (Technical) Section 4.9 Clearing effects of
task management, FCP, FC-FS, and FC-AL-2 actions and Section 6.3.4 New
or repeated PRLI

<excerpts from FCP-2> Section 4.9 Clearing effects of task management,
FCP, FC-FS, and FC-AL-2 actions Table 6 (and maybe 4) does not reflect
working group agreement.

Table 6 - Management of mode pages during PRLI and PRLO
PRLI/shared/other initiators = use saved or default mode pages [00-342r0
requested "unchanged, most current values if no reset"] [discussing
00-342r0, Sep CAP WG agreed on "unspecified" with a note explaining what
"unspecified" means]

Table 4 - Clearing effects of link related functions (excerpt) For
PRLI(8)(13), PRLO Target mode page parameters restored from saved pages
(...) For all initiator ports(12) = N Only for initiator port associated
with the action = Y

Section 6.3.4 New or repeated PRLI After the completion of any new or
repeated binding PRLI, both members of all image pairs successfully
established shall have the same state as they would have after a hard
reset or a power on with respect to each other. All clearing actions
specified in 4.9 shall be performed. Tasks, reservations, status, and
MODE SELECT parameters for other image pairs are not affected.
</excerpts>

According to 00-307r0 Minutes from SCSI CAP 11 Sep 2000: "Jim Coomes
reviewed the issues between FCP-2 process login and proposed that mode
pages not change as a result of process login (00-342r0) unless a power
on reset or target reset also occurred. Bob Snively stated a preference
for making the behavior unspecified. Concerns were raised about readers
not knowing what unspecified means and it was agreed that a descriptive
note is required."

According to 00-300r3 Installation of corrections in FCP-2, item 4.115:
IBM comment from George Penokie (Editorial) "Page 14 - table 5 - The two
entries labeled 'discard current mode pages' should be changed to 'not
specified'. There is no reason to force the device to discard current
mode pages or do any other action with mode pages at this point.
Response: Accepted. See 6.51. Installation: Installed as requested. Note
that T10-00-342r0 (Clearing affects on other initiators, by Jim Coomes)
also references this issue. At the time, the thought was to specify the
PRLI unshared case as "unspecified", but after further study, I have
used "use saved or default mode pages". Approved October 30, 2000."

00-342r0 requested a change in the "PRLI/shared/none logged in" row, not
the "unshared" row. I assume that "PRLI unshared case" was meant to be
"PRLI shared/none logged in" in the 00-300r3 resolution comment.

The issue is that an initiator probably doesn't know if other initiators
happened to be logged in or not, so it always has to check shared mode
pages after logging in. Forcing the target to revert to saved/default
pages on either last logout or first login doesn't help anything. Many
existing FCP targets preserve mode pages, and a change in FCP-2 that
adds no value but makes existing devices noncompliant should be avoided.

With non-shared pages, the initiator does know the full state of the
target with respect to its page, so full specification is helpful. The
value after logout doesn't matter, because the initiator cannot
accessing the target without a new login. Thus specifying that pages are
reset after login is adequate.

00-342r0 suggested mentioning reset as a special case. That is covered
in table 4, so the issue can be ignored in table 6.

Table 6 should use "not specified" for the "PRLI/shared/none logged in"
case.

Table 4 should refer entirely to table 6 for the "only for initiator
associated with the action" row, rather than trying to apply a "Y" or
"N" to them. "Saved or default" means "Y," "not specified" means
"maybe", and "maintain current" means "N."

The first sentence of Section 6.3.4 needs this added: "except for mode
page parameters (see table 6)."

Response:

Three changes are requested by this comment:

1) Table 6 change:

	Proposed change is: Table 6 should use "not specified" for the
"PRLI/shared/none logged in" case.

	Action: No change is made. In the October meeting there was a
strong consensus that, if there are no active process logins with a
device, it is reset. The expected behavior after exiting from such a
reset when the PRLI is performed is that the device is in a known and
expected state, the default or saved state.

	After further study, the working group chose to use the term
"not specified" for this case in a vote of 7 in favor, 2 against, and 2
abstaining in the meeting of January 15, 2001.

	Installation:

	Installed as voted. For the record, let me state that I think
this is a really bad solution that will come back and haunt us. It is
likely that profile statements will be required to correct this. I
believe that it is a direct and non-negotiable violation of SCSI-2,
8.2.10.2 and SPC-2, 7.11.2. Note that the clearing and management of
mode pages is not specified in SAM-2, SPI-3, or SPI-4.

2) Table 4 change:

	Proposed change is: Table 4 should refer entirely to table 6 for
the "only for initiator associated with the action" row, rather than
trying to apply a "Y" or "N" to them. "Saved or default" means "Y," "not
specified" means "maybe", and "maintain current" means "N."

	Action: Table 6 only references PRLI and PRLO, not failed
discovery. Those two cases have their "Y" and "N" indications replaced
with a note referencing table 6, but the failed discovery cases remain
unchanged.

	After further study, the working group chose to replace the Y
and N values in this location of the tables with dashes containing a
super-script reference to note 12, which references table 6. This
resolution was approved in the meeting of January 15, 2001.

	Installation:

	The change was made for the two locations associated with the
two mode select page rows and the PRLI/PRLO column. The superscript
notes were removed from the two mode select page row definitions in both
table 4 and 5. Please review for completeness.

Section 6.3.4, first sentence change:

	Proposed change is: The first sentence of Section 6.3.4 needs
this added: "except for mode page parameters (see table 6)."

	Action: Accepted. The first sentence is changed accordingly.
This action was approved in the January 15, 2001 meeting.

	Installation:

	Installed as requested. For the record, let me state that I
think this is a really bad solution that will come back and haunt us. It
is likely that profile statements will be required to correct this. I
believe that it is a direct and non-negotiable violation of SCSI-2,
8.2.10.2 and SPC-2, 7.11.2. Note that the clearing and management of
mode pages is not specified in SAM-2, SPI-3, or SPI-4.


Bob Snively                        e-mail:    rsnively at brocade.com
Brocade Communications Systems     phone:  408 487 8135
1745 Technology Drive
San Jose, CA 95110



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 Note my comments at the end, where I indicate my dissatisfaction with the agreed-upon solution.  This is likely to come back and haunt us in no uncertain terms.  Customers who demand this of their vendors should be either educated or provided with an explicitly non-standard product.  The standard product should have a defined current value after a first PRLI with shared mode pages equal to the saved or default values, as specified by SCSI-2, SPC, and SPC-2.  Fudging this to be vendor specific is a really bad idea. I am soliciting correction of this at the FCP-2 meeting in March.  It is installed as shown below for now. Bob   2.3  Consideration of mode pages, technical CPQ-003: PDF 33, Page 19 (Technical) Section 4.9 Clearing effects of task management, FCP, FC-FS, and FC-AL-2 actions and Section 6.3.4 New or repeated PRLI <excerpts from FCP-2> Section 4.9 Clearing effects of task management, FCP, FC-FS, and FC-AL-2 actions Table 6 (and maybe 4) does not reflect working group agreement. Table 6 - Management of mode pages during PRLI and PRLO PRLI/shared/other initiators = use saved or default mode pages [00-342r0 requested "unchanged, most current values if no reset"] [discussing 00-342r0, Sep CAP WG agreed on "unspecified" with a note explaining what "unspecified" means] Table 4 - Clearing effects of link related functions (excerpt) For PRLI(8)(13), PRLO Target mode page parameters restored from saved pages (...) For all initiator ports(12) = N Only for initiator port associated with the action = Y Section 6.3.4 New or repeated PRLI After the completion of any new or repeated binding PRLI, both members of all image pairs successfully established shall have the same state as they would have after a hard reset or a power on with respect to each other. All clearing actions specified in 4.9 shall be performed. Tasks, reservations, status, and MODE SELECT parameters for other image pairs are not affected. </excerpts> According to 00-307r0 Minutes from SCSI CAP 11 Sep 2000: "Jim Coomes reviewed the issues between FCP-2 process login and proposed that mode pages not change as a result of process login (00-342r0) unless a power on reset or target reset also occurred. Bob Snively stated a preference for making the behavior unspecified. Concerns were raised about readers not knowing what unspecified means and it was agreed that a descriptive note is required." According to 00-300r3 Installation of corrections in FCP-2, item 4.115: IBM comment from George Penokie (Editorial) "Page 14 - table 5 - The two entries labeled 'discard current mode pages' should be changed to 'not specified'. There is no reason to force the device to discard current mode pages or do any other action with mode pages at this point. Response: Accepted. See 6.51. Installation: Installed as requested. Note that T10-00-342r0 (Clearing affects on other initiators, by Jim Coomes) also references this issue. At the time, the thought was to specify the PRLI unshared case as "unspecified", but after further study, I have used "use saved or default mode pages". Approved October 30, 2000." 00-342r0 requested a change in the "PRLI/shared/none logged in" row, not the "unshared" row. I assume that "PRLI unshared case" was meant to be "PRLI shared/none logged in" in the 00-300r3 resolution comment. The issue is that an initiator probably doesn't know if other initiators happened to be logged in or not, so it always has to check shared mode pages after logging in. Forcing the target to revert to saved/default pages on either last logout or first login doesn't help anything. Many existing FCP targets preserve mode pages, and a change in FCP-2 that adds no value but makes existing devices noncompliant should be avoided. With non-shared pages, the initiator does know the full state of the target with respect to its page, so full specification is helpful. The value after logout doesn't matter, because the initiator cannot accessing the target without a new login. Thus specifying that pages are reset after login is adequate. 00-342r0 suggested mentioning reset as a special case. That is covered in table 4, so the issue can be ignored in table 6. Table 6 should use "not specified" for the "PRLI/shared/none logged in" case. Table 4 should refer entirely to table 6 for the "only for initiator associated with the action" row, rather than trying to apply a "Y" or "N" to them. "Saved or default" means "Y," "not specified" means "maybe", and "maintain current" means "N." The first sentence of Section 6.3.4 needs this added: "except for mode page parameters (see table 6)." Response: Three changes are requested by this comment: 1) Table 6 change: Proposed change is: Table 6 should use "not specified" for the "PRLI/shared/none logged in" case. Action: No change is made. In the October meeting there was a strong consensus that, if there are no active process logins with a device, it is reset. The expected behavior after exiting from such a reset when the PRLI is performed is that the device is in a known and expected state, the default or saved state. After further study, the working group chose to use the term "not specified" for this case in a vote of 7 in favor, 2 against, and 2 abstaining in the meeting of January 15, 2001. Installation: Installed as voted. For the record, let me state that I think this is a really bad solution that will come back and haunt us. It is likely that profile statements will be required to correct this. I believe that it is a direct and non-negotiable violation of SCSI-2, 8.2.10.2 and SPC-2, 7.11.2. Note that the clearing and management of mode pages is not specified in SAM-2, SPI-3, or SPI-4. 2) Table 4 change: Proposed change is: Table 4 should refer entirely to table 6 for the "only for initiator associated with the action" row, rather than trying to apply a "Y" or "N" to them. "Saved or default" means "Y," "not specified" means "maybe", and "maintain current" means "N." Action: Table 6 only references PRLI and PRLO, not failed discovery. Those two cases have their "Y" and "N" indications replaced with a note referencing table 6, but the failed discovery cases remain unchanged. After further study, the working group chose to replace the Y and N values in this location of the tables with dashes containing a super-script reference to note 12, which references table 6. This resolution was approved in the meeting of January 15, 2001. Installation: The change was made for the two locations associated with the two mode select page rows and the PRLI/PRLO column. The superscript notes were removed from the two mode select page row definitions in both table 4 and 5. Please review for completeness. Section 6.3.4, first sentence change: Proposed change is: The first sentence of Section 6.3.4 needs this added: "except for mode page parameters (see table 6)." Action: Accepted. The first sentence is changed accordingly. This action was approved in the January 15, 2001 meeting. Installation: Installed as requested. For the record, let me state that I think this is a really bad solution that will come back and haunt us. It is likely that profile statements will be required to correct this. I believe that it is a direct and non-negotiable violation of SCSI-2, 8.2.10.2 and SPC-2, 7.11.2. Note that the clearing and management of mode pages is not specified in SAM-2, SPI-3, or SPI-4. 
Bob Snively                        e-mail:    rsnively at brocade.com
Brocade Communications Systems     phone:  408 487 8135
1745 Technology Drive
San Jose, CA 95110


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