Gentlemen,
I am sending back the summury of responses I got for my questions about
the Fast Wide interfaces on Turbo Channels:
- Number of these boards per machine: Depends of the machines, the
detail follows in Thomas P. Blinn's mail.
- How many devices (disks) per FWD bus ? currently 7, 15 after the
version 3.2 of OSF1 is released.
I would really like to thank the three DEC engineers who responded,
Thomas P. Blinn from New Hampshire center, Greg R. Sorensen from MI,
and Alan Rollow for their fast and objective responses.
Regards,
Felix.
--------------------------------
Subject: Re: Fast-Wide SCSI on TurboChannel bus
> Has anybody ever installed a Fast Wide SCSI board on a Turbo Channel bus
> in a DEC 3000 machine ? I would like to know several things before we purchase
> such a board(s):
>
> - How many disks does it support on such a bus ( theoritically 15
> but I have heard about possible problems when the number of disks exceeds the
> usual 7 devices for OSF1 software problem )
>
> - How many of these boards are supported inside a single machine ?
>
> I asked this questions to both the DEC local marketting and technical teams,
> and I got different responses....
Many people have done so, although I personally have not.
The present DEC OSF/1 device naming scheme limits you to 7 devices per SCSI
bus, although the bus itself could support more. This is supposed to change
in a future release of DEC OSF/1 (perhaps by the end of calendar 1995) but
it is a limitation at present. Since the boards have two buses per board
(for the PMAZC-AA), you can support 14 devices per board. If you're talking
about the KZTSA-AA, it only has one SCSI bus you can use to support up to 7
devices.
The number of boards supported in a single machine depends on the machine.
For instance, the DEC 3000 Model 300L, although using a TURBOchannel bus
internally, has NO place to mount such an option.
In the DEC 3000 Models 400, 600, and 700 (big desktop workstations) you can
mount at most 3 boards, but since one of the TURBOchannel slots (at least)
must be used for the graphics adapter, you can only add two PMAZC-AA SCSI
adapters, and two is the supported limit. In the server configuration (no
graphics), you can put in three and three are supported.
In the DEC 3000 Models 500, 500X, 800, and 900, there are more slots that
can be used for TURBOchannel options, and these systems support up to five
(according to the catalog) SCSI option cards.
Get the current Digital Systems and Options catalog from your local sales
office. It has the configuration rules. You need to know what system you
are going to try to do this with (you didn't say) and which option card (you
didn't say).
Tom
Dr. Thomas P. Blinn, UNIX Software Group, Digital Equipment Corporation
110 Spit Brook Road, MS ZKO3-2/U20 Nashua, New Hampshire 03062-2698
Technology Partnership Engineering Phone: (603) 881-0646
Internet: tpb_at_zk3.dec.com Digital's Easynet: alpha::tpb
Worry kills more people than work because more people worry than work.
My favorite palindrome is: Satan, oscillate my metallic sonatas.
-- Phil Agre, pagre_at_ucsd.edu
Opinions expressed herein are my own, and do not necessarily represent
those of my employer or anyone else, living or dead, real or imagined.
From: sorensen_at_det.dec.com
Felix,
The KZTSA (TURBOchannel FWD SCSI) is a good board. It is an intelligent SCSI
controller, and unlike some other SCSI boards, it does not use much of the CPU
for processing data even in heavy I/O situations. In theory, it can support
up to seven devices, each of which could be a device known as an HSZ40. The
HSZ40 is an intelligent RAID controller, supporting RAID 0,1,3, and 5. It
also supports redundant controller failover, hot swap of disks, standby disks,
etc. Each HSZ40 supports six device arrays, each of which can have six devices.
Thus we get 6 x 6 x 7 = 252 devices per KZTSA. With 2.1 GByte drives this is
a little over 1/2 a Terabyte per TURBOchannel slot. With the newer 4.3 GByte
drives we are beginning to sell, it would be over 1 TByte per KZTSA. You can
have as many KZTSA's as you have TURBOchannel slots.
Now there are some additional issues which will impose real world limits on
this theoretical maximum. SCSI cable length limitations will make it very
difficult to actually cable up that much storage. Also, there are some
current limits on how many devices DEC OSF/1 can recognize, though this can
be hidden by the RAID controller (i.e. instead of presenting 42 individual
drives to the system, it could present them as 1 huge device). Finally, you
may not get the performance you want in a heavily I/O loaded situation with
that many drives per KZTSA board.
At this time even on a FWD controller, we can only recognize up to seven
directly attached devices, such as a disk or a RAID controller. Support for
additional devices (up to the theoretical limit of 15) will be provided in
upcoming releases of the operating system and the controllers / drives.
This requires 16 bit support throughout the system, and we are not quite
there yet.
Please confirm this information with your local account team *before* sending
us an order, as I am not quite infallible.
Regards,
Greg
===============================================================================
Greg R. Sorensen sorensen_at_det.dec.com
Open Systems Consultant Office: (810) 347-5394
Digital Equipment Corporation Fax: (810) 347-5334
39500 Orchard Hill Place Pager: (800) SKY-PAGE
P.O. Box 8017 PIN# 4722973
Novi, MI 48376-8017 Cellular: (313) 418-8102
From: alan_at_nabeth.cxo.dec.com (Alan Rollow - Dr. File System's Home for Wayward Inodes.)
Subject: Re: Fast-Wide SCSI on TurboChannel bus
OSF has a limit of 7 targets on the bus, whether it is
wide or not. Rumor has this will be fixed in some future
version after V3.2.
I haven't seen any limits on the number of controllers
per systems, so it is probably only limited by the number
of slots. The configuration file is well prepared for
at least six.
-------------------------------------------------------------------------
Felix Hassine
CORE group | E-mail : acher_at_sun2.cern.ch
CN division CERN | Phone: (19 41 22) 767 94 56
1211 Geneve 23 | Beep : 13+5546
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Received on Tue Feb 14 1995 - 12:19:20 NZDT