[dba-Tech] wXP virtual memory question

John Bartow john at winhaven.net
Thu Jan 13 00:33:57 CST 2005


Jon,
I think the speed and size of HDs somewhat alleviates much of the problem of
paing. However IIRC the pagefile is a "file system" of its own inside a
file. In other words it has to index where it puts all the swapped out info.
Knowing how poorly the Windows OS places files on the file system (hence the
need for defraggers) I can't imagine that it is any better in the swap file
system space. So, by oversizing the pagefile one may be slowing down the
response time because of the seek time. I realize I'm getting a bit
nit-picky here but after all we are talking about overriding the original
programmers specifications here for the sake of tweaking the best
performance out of Windows. And I thought I should raise the flag for this
one :o)

Try this approach once and see what you would have to set it to.

Use your computer for the day. Before shutting it down close all, open the
task manager, look at the performance tab, look at the peak usage of memory
near the lower left corner.

Calculate: peak usage (in KB)/1024 - total physical memory in MB = pagefile
maximum usage in MB

Round "pagefile maximum usage in MB" up to the nearest 50MB

Set your "Pagefile" or "Virtual Memory's" "Initial" and "Maximum" sizes to
that value and you should get the maximum performance.

If you change the way you use your computer (bigger files, different
programs, more programs at once) you should redo this. You may even want to
do this over a week or two and take the highest value. 

John B. 

 


-----Original Message-----
From: dba-tech-bounces at databaseadvisors.com
[mailto:dba-tech-bounces at databaseadvisors.com] On Behalf Of Jon Tydda
Sent: Wednesday, January 12, 2005 10:29 AM
To: 'Discussion of Hardware and Software issues'
Subject: RE: [dba-Tech] wXP virtual memory question

When I did my course, they said anything between 1.5 times and 2.5 times the
amount of RAM you have installed is correct, which is what windows allocates
automatically - 1.5 times as the lower limit and 2.5 times as the upper. We
were told that if we kept both numbers the same, then performance wouldn't
degrade when more of the page file was used, as you wouldn't have to wait
for the page file to resize itself. This was a couple of years ago... maybe
with the advent of SATA or the 10,000 rpm drives it's not so much of an
issue. Sometimes I get messages saying that I've run out of memory, even
wiuth 1gb of ram and 2gb pagefile on my pc at work, which concerns me
slightly, especially when I'm only using Excel, and not in a hardcore way...


Jon

-----Original Message-----
From: John W. Colby [mailto:jwcolby at colbyconsulting.com]
Sent: 12 January 2005 14:18
To: 'Discussion of Hardware and Software issues'
Subject: RE: [dba-Tech] wXP virtual memory question


>I have heard or read that the pagefile.sys setting should be twice the 
>RAM
available.

I tend to build a dedicated partition which is 1.5 times the max size my
memory could possibly be (biggest the machine can handle), then place the
swap file on that drive and never store anything else on it.  I then allow
the system to manipulate the page file as it sees fit.  One big issue with
the page file is fragmentation on a normal drive, if it is used at all (and
it may not be if you have enough memory) then the page file gets fragmented
just like any other file if it is out on a regular partition.  Having to hit
the page file at all is enough of a drag on the system without the
additional slow down of a fragmented page file.

By placing it on it's own partition, then it expands and contracts linearly
with no fragmentation.  I have also heard however that if you use the
dedicated partition trick, just set the page file to the size of the
partition.  It then will build the page file one time and never "take time"
later to expand or contract the file.  Or I guess just do as Jon mentioned
and set the two numbers to the same size.

The hiberfile can be killed since once you are loaded it is not in use.
When it hibernates, it will create a new one.  AFAICT you can't determine
where that file is created.  The file is a literal "memory dump" of the
state at the time the computer is closed.  The idea is to read memory as if
it were a big PROM, load this big PROM into ram as the system comes up and
then execute out of the "PROM".  The PROM of course is all of the programs
that you had loaded at the time you shut down.  It works just fine on my
laptop, though I must admit that I do perform a normal close / open cycle
occasionally just for drill so to speak.

John W. Colby
www.ColbyConsulting.com 

Contribute your unused CPU cycles to a good cause:
http://folding.stanford.edu/

-----Original Message-----
From: dba-tech-bounces at databaseadvisors.com
[mailto:dba-tech-bounces at databaseadvisors.com] On Behalf Of Arthur Fuller
Sent: Wednesday, January 12, 2005 8:31 AM
To: Discussion of Hardware and Software issues
Subject: [dba-Tech] wXP virtual memory question


Actually, three related questions:

1. The interface is quite quite confusing (or alternatively, my senior
moments are becoming more frequent). I want to move the Windows pagefile.sys
from drive e: to drive f:. It's not readily apparent how to do this.

2. I have heard or read that the pagefile.sys setting should be twice the
RAM available. Is this just old-folks' tales or is there sense behind this
alleged maxim?

3. I just noticed another file 260MB large called hiberfil.sys. What is
this? Can I kill it? Can I move it?

TIA,
Arthur

>  
>


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