Vax 11/780 performance vs Sun 4/280 performance

[John F. Haugh II]

In article <7331 at swan.ulowell.edu> arosen at hawk.ulowell.edu (MFHorn) writes:
>In article <601 at modular.UUCP> olson at modular.UUCP (Jon Olson) writes:
>> there is a knee in the performance curve of the Sun-4/280 at > 15 processes
>> And the Sun-3's are no better: the knee there is >7 processes.
>
>Some time ago I saw a Sun 3/280 with a load average of 17+.  There were
>17 'extra' jobs running.  I don't know what they were doing (they weren't
>mine), but there was no [noticable] degradation in response time at all.

our plexus p/95 (20MHz 68020, vme bus, 8MB ram, esdi controller) knees at
about 20 users with a load average of 10+.  on the few occasions the
machine has been to 13+ it has crashed shortly thereafter.

the p/55 (12.5MHz 68020, multi bus, 4MB ram, scsi? controller) knees at
about 10 users.  i don't know the load average off hand but it has been
up around 10 without crashing.  it just gets painfully slow.

i suggest the Big Problem is with the disk/controller combinations.  my
'386 can't run an expire and an rn together because the disk saturates.
same seems to be true with the plexus machines.  the p/55 has a single
controller and a single drive.  the p/95 has a single (faster) controller
with two drives.  once the i/o on either plexus is saturated (the famous
popcorn noise is my general working definition), regardless of the number
of processes, adding one more serious dogs the system.

- john.
-- 
John F. Haugh II                 | "If you aren't part of the solution,
River Parishes Programming       |  you are part of the precipitate."
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DOMAIN: jfh at rpp386.uucp          |