Re: How do I determine appropriate swapspace settings? And other partitioning questions.

From: Paul Sherwin (paulSPAM_at_paulsherwin.co.uk)
Date: 02/08/05 

Date: Tue, 08 Feb 2005 21:11:23 GMT

On , Morningdew <yahooaddyismorning42dew@spam.free> wrote:
>
>I was just curious to know... What are some good rules of thumb for
>configuring swap space under Linux? For that matter, are there any
>comprehensive guides or articles on the subject? When I used to admin
>NT boxes I used to set their "virtual memory" setting to 1.5 times
>physical memory, giving 50% over physical as swap. That was just by
>convention, or, "rule of thumb". No great scientific methodology, it is
>just what had worked for me and my coworkers for so long. Granted,
>Linux is different.

There is *no* direct relationship between physical memory and swapfile
size. These rules of thumb originated in the 70s when people had to
commission systems before knowing what the application mix would be.
The idea was that a system with a lot of memory would be used for
memory intensive applications, so should have a lot of swapspace as
well. Some systems also used swapspace to hold a memory dump in the
event of a system crash, so the swap had to be at least as large as
physical memory.

Modern Linux systems with lots of physical memory will almost never
swap, unless you're doing something very unusual. If you find the
system is swapping a lot, you should add more physical memory rather
than fiddling around with swapspace, My main Linux server is currently
using 778k of swapspace, and this is quite typical. Despite this,
people keep configuring gigabytes of swapspace.

You can always add a swap file later, which will keep you going until
you upgrade memory.

HTH, Paul 

--
Paul Sherwin Consulting     http://paulsherwin.co.uk

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