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| d | i | g | i | t | a | l | TIME DEPENDENT BLITZ
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BLITZ TITLE: BA356 enclosures, RZ29B's, RZ28D's , DWZZB-VW's
and SWXA2-BA (MVD)
DATE: November 1, 1996
AUTHOR: Charles Schnare TD #:
DTN:237 3639
ENET:SUBSYS::SCHNARE CROSS REFERENCE #'s:
DEPARTMENT: Adapters and Backplane (PRISM/TIME/CLD#'s)
Controllers Engineering
INTENDED AUDIENCE: U.S/EUROPE/GIA PRIORITY LEVEL: 1
(1=TIME CRITICAL,
2=NON-TIME CRITICAL)
=====================================================================
Subject : BA356 enclosures, RZ29B's. RZ28D's , DWZZB-VW's and SWXA2-BA (MVD)
PROBLEM OVERVIEW:
-----------------
Storage BA356 enclosures using a combination of AC power supplies,
DWZZBs, and RZ29Bs or RZ28Ds can exhibit SCSI command time-outs. The
result of these time-outs is interrupted I/O between the subsystem
and the host.
CONFIGURATIONS AFFECTED:
------------------------
The specific configurations that could be affected are as follows;
1) BA356 enclosures, utilizing AC power supplies, and a
combination of one (1) DWZZB-VWs and four (4) or more
RZ29Bs or RZ28Ds.
2) BA356 enclosures, utilizing AC power supplies, and a
combination of two (2) DWZZB-VWs and three (3) or more
RZ29Bs or RZ28Ds.
TECHNICAL DETAIL:
-----------------
In the above mentioned subsystem configuration, the cumulative
voltage drops across the subsystems power distribution system
(which includes the power supply, backplane, loads, flex circuit,
and DWZZB-VW itself) can cause the low voltage sensor on the DWZZB-
VW to trigger. This will cause the SCSI bus to go into a bus free
state on the target side, resulting in SCSI bus command time-outs.
The nature of the problem is such that some of these configurations
will in fact operate error free.
AFFECTED SERIAL NUMBER RANGE: N/A; Rev A02 DWZZB-VW units.
Rev A02 SWXA2-BA (MVD)
Short Term Work Arounds:
------------------------
Corrective action is only required IF you have a storage subsystem
matching the above configurations AND it is exhibiting the system
symptoms described above. There are two proposed work arounds.
1. Add a Second Power Supply. We have found that in most cases
adding a second power supply will correct the problem.
2. Depopulate the BA356 enclosures to one (1) DWZZB-VW and
four (4) RZ29Bs or RZ28Ds or depopulate BA356 enclosures
with two (2) DWZZB-VW's and three (3) RZ29Bs or RZ28Ds.
Long Term Solution:
-------------------
Corrective action is only required IF you have a storage subsystem
matching the above configurations AND its exhibiting the system
symptoms described above. There is one long term solution.
1. Replace the Rev A02 DWZZB-VW units with, Rev B01 DWZZB-VW.
NOTE: This ECO work has just started in manufacturing. It will be
some number of weeks before ECO'd units will be available at
your local field service stockrooms. Short term solutions
listed above will correct the problem until there is
availability in the field service stockrooms.
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