openstack team mailing list archive

[Jay Pipes <jaypipes@xxxxxxxxx>]

On Thu, Dec 15, 2011 at 2:55 PM, Ewan Mellor <Ewan.Mellor@xxxxxxxxxxxxx> wrote:
> Your simulation is of the one case that I said would work: when you have enough RAM to cache the entire image.
>
> When you _don't_ have enough RAM, then the images will just immediately be evicted, and the performance with the cache will be worse, not better.  This break point is going to be when your cloud has ~20 gold images, which doesn't sound very many to me.

I'll go ahead and benchmark it on some real world systems and get some
hard numbers so we can discuss facts over opinions. If it turns out
that turning off the default cache flushing behaviour leads to an
increase in performance and throughput for a very common use case (as
I believe I have described in this thread...) I hope you won't mind
having a switch to control the cache flush behaviour...

Cheers,
-jay