Jerry McAllister wrote:
On Thu, Nov 09, 2006 at 05:26:38PM +0000, Alex Zbyslaw wrote:
Jerry McAllister wrote:
On Thu, Nov 09, 2006 at 06:39:50AM +0100, VeeJay wrote:
Maximum space required for SWAP to get high performance.
If you end up using swap space you will *not* get performance. The
second you start swapping is the second that your performance goes into
a downward spiral, especially with multi-user servers.
Sort of, but don't forget paging.
The system always pages - pushes out pages that don't get used
so often, but are still part of the active processes. The
system pages to swap space. Paging and possible core dumps
are the main uses of swap space, not actual swapping.
Sure. I should probably have said "If you end up using swap space for
swapping ..."
I wasn't advocating not having any swap space, just pointing out that
maximizing swap space in no way maximized performance of a multi-user
server, just made it's death from overwork that much more drawn out.
There are certainly uses for swap space, but generally the least
desirable usage is swapping. Maximizing swap space won't improve any
paging usage, though splitting it across multiple disks might, and once
you get a core dump you don't exactly have maximum performance either ;-)
Personally I still go by the hoary old rule of thumb - 2x RAM, or even
4x RAM to allow for possible upgrades. But if I actually used it for
swapping on a regular basis I'd be looking at the price of larger memory
sticks - or writing the software more efficiently :-)
--Alex
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