[CentOS] Swap priorities with swapon (Is my swap drive working?)

James Bensley

jwbensley at gmail.com
Fri Jun 5 07:32:42 UTC 2009


Hey Listee's

I have a CentOS server with 2GB of ram and a swap drive of 4GB;

swapon -a shows my swap drive as 4GB with only about 350 bytes in use
(which is fine as my server idles with about 350-400MB ram usage so no
swap should be in use. However my one and only swap drive had a
priority of -1. I had read that the swap drive priority doesn't matter
too much because I only have one swap drive so the kernel hasn't got
to make a choice but also that after a certain kernel version (which
is think was like 1.3.x?) it didn't even use the priority value and my
kernel is newer (I have 2.6.18-128.1.6.e15).

Basically I have read difference things from difference source on the
old interwebwrok and seek clarification. In the confusion I set my
swap drive priority from -1 to 1 because I thought that if the drive
priority were a negative value it might not actually use the swap
drive. Ultimately I can't tell because there currently isn't enough
memory usage demand on the server.

On a side note: I'm a reformed Windows admin and have seen the light
and am moving each server one at a time over to Linux so I am used to
poor memory management and needing massive page files. Realistically
the swap drive shouldn't been in use but I am just worried then when
this server goes live it will hit 2GB of ram usage and the swap won't
kick in. Is there anyway I can check?

Thanks for reading.

Regards,
James ;)

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