Seeking clarification on Threshold Out/In diagnostic pages

Elliott, Robert (Server Storage) Elliott at hp.com
Thu May 31 12:02:50 PDT 2012


Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r1205313_f.htm">HTML-formatted message</a>

The Threshold Out/In diagnostic pages are old, and just report 4 bytes per
element type plus 4 bytes per individual element; the Additional Element
Status diagnostic page is relatively new and is designed to return a lot more
data per element (but not all elements need to report extra data).  So, don't
be surprised by differences.
These are all the same size:
- control descriptor list (Enclosure Control diagnostic page)
- status descriptor list (Enclosure Status diagnostic page)
- threshold control descriptor list (Threshold Out diagnostic page)
- threshold status descriptor list (Threshold In diagnostic page)
In ses3r04a, table 65 and table 66 (PDF page 85-86) define the generic
formats for the threshold elements.  I agree there should be a statement
somewhere that:
a) all the fields in the threshold control elements are ignored; and
b) all the fields in the threshold status elements are reserved,
for the elements listed in table 60 (PDF page 82) as having a threshold of
"none".
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Raj Divecha
Sent: Friday, 04 May, 2012 3:37 PM
To: Matthew_Jacobs at Dell.com
Cc: t10 at t10.org
Subject: RE: Seeking clarification on Threshold Out/In diagnostic pages
Matt,
Yeah that's a strong indicator indeed, I too acknowledge that in my email.
However, those placeholder/reserved threshold elements are a huge wastage and
amounts to unnecessary data being transferred. Thus I believe that the
authors of the SES spec wouldn't have intended the same and is a thing that
does not clearly come out of the spec.
Consider the below given configuration of an imaginary enclosure. In this we
are talking about sending/receiving 352 bytes of useless data, that is
approximately 80% wastage. The number of useless bytes would almost multiply
as you add subenclosures.
24
Array Device Slot elements
2
Power Supply elements
6
Cooling elements
4
Temperature Sensor elements
1
Door Lock element
1
Audible Alarm element
2
Enclosure Services Controller Electronics elements
1
Invalid Operation Reason element
1
UPS element
1
Display element
1
Enclosure element
6
Voltage Sensor elements
4
Current Sensor elements
2
SAS Expander elements
30
SAS Connector elements
2
VS element 1
4
VS element 2
As the authors limited the number of element types appearing in the
Additional Element Status diagnostic page, it is probable that they intended
the same for the Threshold Out/In diagnostic page but unfortunately it didn't
came out that way in the spec.
Raj
From: Matthew_Jacobs at Dell.com<mailto:Matthew_Jacobs at Dell.com>
[mailto:Matthew_Jacobs at Dell.com]<mailto:[mailto:Matthew_Jacobs at Dell.com]>
Sent: Friday, May 04, 2012 1:42 PM
To: Raj Divecha; t10 at t10.org<mailto:t10 at t10.org>
Subject: RE: Seeking clarification on Threshold Out/In diagnostic pages
Raj,
The descriptions of the threshold control descriptor list and the threshold
status descriptor list in sections 6.1.8 and 6.1.9 state that the list
contains a control/status "descriptor for each type descriptor header in the
Configuration diagnostic page".  From that, I believe all individual elements
defined in the Configuration diagnostic page have a threshold element in the
Threshold in/Out diagnostic page even if it is just a placeholder/reserved
threshold element.
Matt
From: owner-t10 at t10.org<mailto:owner-t10 at t10.org>
[mailto:owner-t10 at t10.org]<mailto:[mailto:owner-t10 at t10.org]> On Behalf Of
Raj Divecha
Sent: Friday, May 04, 2012 12:29 PM
To: t10 at t10.org<mailto:t10 at t10.org>
Subject: SES: Seeking clarification on Threshold Out/In diagnostic pages
Hi,
I searched the T10 emails for this but didn't found anything.
The SES spec is a bit ambiguous regarding which element types should be
included in the Threshold Out/In diagnostic page. A clarification would be
helpful.
The following are the excerpts from the 2r20 spec. Below each excerpt is my
comment. The questions are at the end of the email.
6.1.8 Threshold Out diagnostic page
The Threshold Out diagnostic page is transmitted to the enclosure services
process to establish threshold values for those elements that have limited
sensing capability (e.g., temperature sensors, uninterruptible power
supplies, voltage sensors, and current sensors).
My comment: this statement "possibly" suggests that this page includes only
those element types that support threshold.
The threshold control descriptor list contains a threshold control descriptor
for each type descriptor header in the Configuration diagnostic page (see
6.1.2).
My comment: this statement "strongly" suggests that this page includes all
element types, whether or not they support thresholds.
7.1 Element definitions overview, Table 60
My comment: shows which element type support thresholds and which not.
7.2.4 Threshold control element format
All fields in the threshold control element are advisory. The enclosure
services process shall ignore the contents of the threshold control element
for those elements that have no value to be compared with a threshold and for
those elements that do not implement the threshold function.
My comment: this statement suggests that threshold descriptors for even those
element types, that do not support threshold, are included in the Threshold
Out/In diagnostic page, however, the application client and the enclosure
services process (ESP) are supposed to ignore them.
7.3 Field definitions for all element types
My comments: this section does not describe the threshold descriptors for
element types that do not support threshold. Not even a generic descriptor
with 4 reserved bytes is defined.
If the readers are to assume that the threshold descriptors for even those
element types that do not support threshold are to be included in the
Threshold Out/In diagnostic pages, then they are also supposed to assume a
generic 4-byte threshold descriptors with all bytes as reserved as they are
supposed to be ignored by both the application client and the ESP.
If the readers are to assume that the Threshold Out/In pages should include
only those element types that support threshold then there is no question of
assuming a generic 4-bytes reserved descriptor and no question of ignoring
them.
Based on the above there are many "strong" points that indicate that the
Threshold Out/In pages include even those element types that do not support
thresholds and there are some "weak" points that indicate that they don't
include those element types.
Did the spec authors intended to include additional descriptors in the page
that will never be used?
Or were the Threshold Out/In diagnostic pages meant to be similar to the
Additional Element Status diagnostic page where in only a selected subset of
element types appear in these pages?
In my opinion the spec authors did not intend to include additional
descriptors in the page that will never be used and thus the Threshold Out/In
diagnostic page is similar to the Additional Element Status diagnostic page
where only a limited subset of element types appear in these pages. However,
I could be wrong, thus please clarify.
Thanks,
Raj



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