Double 451 controller advantages?

[Allen Sonafrank]

We have a network of 66 Sun 3/50 workstations, mostly diskless, supported
by five Sun fileservers (3/160, 3/160, 3/180, 3/280, 4/280).  Each server
has a single Xylogics 450 or 451 disk controller, with two disk drives.
We are currently running SunOS 3.5 on all but the SPARC server and four
workstations, and are reluctant to upgrade :-) to SunOS 4.0 with our 4mb
workstations.

We are attempting to overcome a serious I/O bottleneck on the servers.
They can't satisfactorily handle the demands placed on them by NFS service
and workstation paging at times of peak load.

Anecdotal evidence leads us to believe that we could solve this problem by
adding additional disk controllers, so that each disk drive was served by
a single controller.

Does anyone have experience which compares machines with two controllers
to machines with a single controller?

What kind of increase in I/O throughput did you notice after doubling up
on Xylogics 450 or 451 (SMD) disk controllers in a server?

Has anyone possibly doubled up on 450/451 controllers, and then later
upgraded to a single Xylogics 7053 (SMD-4) disk controller and OS 4.0?
The increase in throughput is said to be up to 100% over a single 450 or
451.  So such a system should still run faster than one with the old SMD
controllers doubled.  We're thinking that the speed of the Xylogics 7053
might compensate for the increased paging we would expect under SunOS 4.
What has your experience been?

Please reply by email, and I'll summarize.  Thanks much.

+------------------------------------------------------------------------+
| Allen Sonafrank          |                                             |
| System & Network Manager |     allen at qal.berkeley.edu                  |
| QAL, 2220 Piedmont Ave.  |     ucbvax!qal!allen                        |
| University of California |     allen at ucbqal.bitnet                     |
| Berkeley, CA 94720       |                                             |
| (415) 642-9890           |                                             |
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