Re: Several words on File Fragmentation and performance

Tech-Archive recommends: Fix windows errors by optimizing your registry

From: Ron Martell (ron.martell_at_gmail.com)
Date: 12/22/04 

Date: Wed, 22 Dec 2004 22:02:18 GMT

Leythos <void@nowhere.lan> wrote:

>
>There are other files, such as the paging file used by Windows NT=3Fs
>virtual memory subsystem, which can also become fragmented with
>unpleasant implications for performance. The solution to these problems,
>as we will see, it to prevent them from happening by keeping your system
>defragmented.
>

Paging file fragmentation, while not totally irrelevant, is pretty
much a non-issue simply because of the way that paging is done.

  Paging out is done based on lack of usage of each individual page
(4K) and there is no requirement or attempt to ensure that pages moved
out to the paging file are in any way related to each other. So if
100 pages (400k) is being moved from RAM to the paging file these 100
pages could be parts of a dozen or more different applications, device
drivers, Windows components, or data files.

If it is subsequently decided to move more items from RAM to the
paging file the items being moved could again represent parts of many
different items, and it is quite possible in fact even likely that
some pages moved out in the second instance will be from the same
items as were some of the pages moved out in the first instance.

And then when one of these items becomes active again it will be
necessary to reload the paged out pages for that item from the paging
file. This could involve pages moved out in two or more different
paging out operations and therefore the items being paged back in will
not be contiguous even if the paging file is totally unfragmented.

Ron Martell Duncan B.C. Canada 

-- 
Microsoft MVP
On-Line Help Computer Service
http://onlinehelp.bc.ca
"The reason computer chips are so small is computers don't eat much."

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