-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of DamianS Sent: Tuesday, February 27, 2007 1:59 AM To: CentOS mailing list Subject: Re: [CentOS] Swap Considerations
On Tue, 2007-02-27 at 07:36 +0200, Alvin Chang wrote:
On 27/02/07, Feizhou feizhou@graffiti.net wrote:
When I get firefox and thunderbird fired up, memory usage
can go through
the roof so I have allocated 2GB (maximum swap partition
size btw) for
Pardon me, but I just set up a CentOS box with 8GB of swap partition yesterday. Am I misisng something?
Not really. 2GB is (or was) the maximum _safe_ swap partition size. However, I have a system with a 4GB swap part and one with a 3GB swap running CentOS, and they both run fine.
I have heard however, that smaller-sized swap partitions are faster/more efficient. ie. 3x1 GB swap partitions are 'supposed to be' better than 1 x 3 GB partition. So when I'm building new systems, I create a number of 1 GB swap partitions depending upon predicted load, and give them differing priorities.
I've theorized (but never bothered to do some benchmarking or to put into practice) that optimum swap strategy may be to have varying sizes eg. 512 MB with highest priority, then 1 GB, 2 GB and 4GB with lowest priority. But I think that would be 'gilding the lily', for just a 'theoretical' increase in eficiency, as opposed to making a practical difference.
If you have 4 1GB swap partitions of equal priority it will interleave operations between them giving you a RAID0 type effect and increasing overall swap performance.
If you setup swap on top of RAID-1, say with LVM, then this scenario will give you the best performance and be able to continue running in the event of a drive failure.
-Ross
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