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1996-07-10
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SUBJECT : IBM SCSI adapter recall & mirroring/duplexing
DATE : April 26, 1990
FYI # : 050190sh
OS VERSION : 286
REVISION :
SHELL VERSION : n/a
GENERAL INFORMATION : An SE from Businessland Corporate was
trying to do mirroring and duplexing with IBM SCSI adapters
using NetWare 286 & 386. He had problems mounting volumes so
he called us for more information so I contacted Tim Ricker of
software engineering who wrote IBMSCSI.OBJ for 286 NetWare.
PROBLEM : Tim explained that IBM's SCSI adapter was
being recalled because of a problem with the chip set on the card.
The chip set was originally rated to run at 25 megahertz but was
found to corrupt data while returning no error messages. Tim has
been in contact with an IBM engineer who changed the adapter speed
to 20 megahertz and is finding no data corruption at this slower
speed.
SOLUTION : Tim Ricker explained that there are two
different adapters: one that caches and one that does not. The
cache controller has SIMMS on the card. Tim wrote the original
driver (PS2286.ZIP on NetWire) to run on the non-caching adapter
but has since added a few lines of assembly code which will check
for caching abilities and use them if present on the adapter.
Tim says the caching version of the driver may not be available
yet for perhaps a few months. So, if customers try to use the
caching adapter, it will not work with PS2286.ZIP on NetWire.
COMMENTS (optional) : Tim wrote the PS2286.ZIP driver to do
mirroring and duplexing even with IBM's own external disk
subsystem. (......As I understand it, this subsystem can consist
of up to 7 daisy-chained embedded SCSI drives being driven by one
SCSI adapter in the expansion bus.......) But, the hardware must
be configured and installed properly before it will work.
Here's how it goes:
MIRRORING: Setting up mirroring is similar to setting up a Novell/ADIC
DCB except for the terminology is different inside the reference diskette
process. Here is the terminology comparison assuming a DCB and two
embedded scsi drives to be mirrored:
DCB terminology REFERENCE DISK terminology
---------------------- --------------------------
Disk Controller Board Adapter (goes in any slot)
embedded scsi controller Device (embd. scsi cont.)
drive LUN (logical unit)
controller=0, drive=0 Device ID=6, LUN = 0
controller=1, drive=0 Device ID=5, LUN = 0
(...embedded controller or Device ID are set with jumpers...)
(...drive and LUN always=0 on embedded scsi, no jumpers.....)
DUPLEXING: For duplexing, the terminology comparison is the
same as above, but there are additional hardware and software
configuration rules to follow before cold booting from the
hard drive will work. Assuming two Adapters and two embedded
scsi drives on each adapter, their configuration will be the
same as in the mirroring example, except for the following:
When two Adapters are installed in expansion slots 3 and 4
(for example), the cold boot process looks at the slot 3 Adapter
as the primary to boot from. With the expansion slots being
numbered from 1 (leftmost) to 8 (rightmost), with slot 8 being
closest to the power supply box, the leftmost adapter will
always be the PRIMARY adapter. The adapters can be installed
in any slot, but the one on the left will become the primary.
This primary adapter must also be addressed (inside reference
setup) with the lowest I/0 address. For example, a slot-3
adapter could have I/0 address = 3540-3547, and a slot-4 adapter
must have an I/0 address = 3548-3555 or greater. All other
addresses/ID#s are the same as the mirroring example above.
YOUR NAME AND DEPT. : Steve Huntington - NSD
Tim Ricker - Software Engineering
(Check one)
(XX) This information has been verified*.
( ) This is useful information, but has not been verified.