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Re: i-ram vs. tmpfs (was: Re: Mail clustering)

On Wed, Apr 04, 2007 at 11:50:00PM +0000, Andy Smith wrote:
> On Wed, Apr 04, 2007 at 07:10:30PM -0400, Matt Cuttler wrote:
> > OTOH, it'd be interesting to see how this i-ram card would perform as
> > swap space
> If you have 4G of RAM to put in an i-RAM then why would you use it
> as swap?  If your machine swaps, use the 4G as real RAM!


> I'd say the killer application for i-RAM is something like holding
> external journals of other filesystems.

yep, that and postfix (or other MTA) queues.

disk i/o is the main bottleneck in any mail server. if you can offload
that to fast (but battery-backed!), ram-disk then you have a massive
performance gain on a loaded mail server.

BTW, from what i've heard, there isn't much difference between using
an I-RAM as an external journal and using any reasonably fast disk
drive. i.e. using any external journal device gives you most of the
benefit, after that it's diminishing returns. and a new hard disk is a
lot cheaper than an I-RAM. about $50 AUD for a brand-new 80GB drive,
which is about the smallest drive you can get nowadays.

i.e. spend $50 on a new SATA drive for the external journal device
and get 80-90% of the performance improvement that you would get for
spending $500 on a 4GB I-RAM.


craig sanders <cas@taz.net.au>

I figure that if God actually does exist, He's big enough to understand an
honest difference of opinion.
		-- Isaac Asimov

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