CS> I still don't agree with your assessment on this
 CS> for computers with lots
 CS> of RAM (i.e., 32MB RAM or more) and fast CPU chips
 CS> (Pentium or faster).  For instance, a Pentium with
 CS> 64MB RAM being used for heavy disk I/O can probably
 CS> benefit from the larger than 2MB cache size available
 CS> with HPFS386.

 PF> You can always design a test to skew the results in
 PF> the direction you want.

That's true.

 PF> My own tests statisfy me that in all but a few
 PF> isolated (ie: dedicated task PC's) real world
 PF> situations OS/2 always does better with more RAM for
 PF> itself,  than stolen by a vdisk or disk cache.

 PF> I have 32mb of ram, run hpfs386,  and only use a 2mb cache.   Using a
 PF> larger cache will cause more swapping (which is not
 PF> cached at all;  a catch-22 by necessity).

I've got 64MB RAM on this P54C/100 system with a fast SCSI-2 hard drive
(Seagate ST12550N "Barracuda") and was using a 4MB HPFS386 cache.
 I just tried an experiment of increasing it to 8MB.  My project rebuild
time dropped from about 84 minutes to 53 minutes with the larger cache. 
The CACHE386 /STATS also showed an increase in the cache read hit rate from
80% to 95%.  This wasn't a completely "controlled" experiment in
that the source code changed slightly between builds and I might not have
all the same software running, so I'll have to try this again under more
controlled circumstances to be sure about the level of improvement.  But it
does seem that the 8MB cache is getting a much higher read hit rate and
does improve performance on this type of task.

 PF> I think people will see a much larger change in
 PF> performance playing with the write-back times and the
 PF> /CRECL value than they will with a >2mb disk cache.

If you've 16MB RAM or less, I think that is probably almost always true. 
But once you're up in the 32MB+ range, that may not be the case across the
board.  I will say, however, that for VisualAge C++ 3.0 on a 32MB RAM
system, you can't afford much more than a 2MB cache anyway. VAC++ 3.0 is a
major memory pig, even without using Visual Builder. Thankfully RAM prices
have been dropping lately.  I can see that within a couple of years it
might sound so unusual to be using computers with 128MB RAM or more.


--- Maximus/2 2.02