Fast/Slow 6386s

[Paul S. R. Chisholm]

<"Would you like me to summon Data so he could offer a few dozen synonyms?">

In article <1060 at vsi.COM>, droman at vsi.COM (Dave Droman) writes:
> I have a customer who is running two (almost) identical 6386 16Mz systems.
> One has a 135MB ESDI drive and the other has a 40MB ST506 drive; both have
> 4MB RAM.
> 
> Both the systems are running ix386 and VP/IX and the identical applications.
> The 40MB is "blowing the doors off" the 135MB.  Indeed, DOS applications under
> VP/IX are actually reasonable on the 40.  

I certainly imagine that, all other things being equal, the EDSI drive
should be much faster than the ST-506.  The most obvious thing that's
*not* equal is the size of the disks.

Maybe it's the layout of the file systems?  Ideally, you should keep
all of your most frequently accessed files (and file systems) near one
another on the disk.  If the big disk is divided up into lots of large,
mostly empty file systems, the head will spend a lot of its time
travelling over unused tracks.  Unfortunately, I can't think of a good
way to measure this; and fixing this involves backing up and restoring
most of your hard disk.

The other thing to check is how well-cached the disks are.  If the 40M
system is setting a lot of RAM aside for the disk cache, I'd expect it
to really hum.  (Make sure they both have all 32-but memory, too.  Just
a thought.)

> David C. Droman				      {uunet!attmail}!vsi!droman
> V-Systems, Inc.				              droman at vsi.com
> (714) 545-6442                                           GREEAAT!!!

Paul S. R. Chisholm, AT&T Bell Laboratories, att!pegasus!psrc
psrc at pegasus.att.com, AT&T Mail !psrchisholm
I'm not speaking for the company, I'm just speaking my mind.