Re: Swap space for kvm virtual host

[John R Pierce <pierce@xxxxxxxxxxxx>]

On 03/14/11 4:45 PM, Nataraj wrote:
> Do you have any sense of whether this takes a big performance hit with
> software raid?  (I was actually planning on hardware raid but the system
> got ordered incorrectly).

if you have adequate memory for your workload, very little data gets 
written to swap, and what is written is done in the background so its of 
little importance to performance.

if your swap is mirrored, writes have to be done to both devices, while 
reads can be load balanced across them, so the write performance is 
equivalent to a single disk, while the read performance in aggregate may 
be twice as fast as a single drive.

if you DONT have adequate memory for your workload, your performance 
will suck pretty badly regardless of how fast the swap device(s) are.


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