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Re: AW: [Xen-users] Use hard drive as physical mem for xen vm

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Subject: Re: AW: [Xen-users] Use hard drive as physical mem for xen vm
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Fri, 11 Nov 2005 14:22:37 +0000
Cc: 'Ernst Bachmann' <e.bachmann@xxxxxxxx>, "Oliver Neumann \[New Identity AG\]" <oliver.neumann@xxxxxxxxxxxxxx>
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> No, with that amount of data in our databases we already calculated, that
> we need at least 4GB only for each cluster node, so we woul dhave to buy at
> least 8GB of ECC RAM which isn't really cheap. The 'problem' is that we
> only need to test an application on a cluster, after that we don't need
> that big amount of memory in that machine so the money is somehow wasted.
> As for the performance: That is irrelevant, the cluster does not need to be
> fast (it actually can be damn slow!).
> Unfortunately there seems to be no chance to save the money using Xen with
> harddisc emulated physical RAM, right?

Can you really not configure MySQL to have a smaller RAM footprint?

If you really want to be evil, you could configure a 4Gig domain, start MySQL 
and then *balloon* it down to 2Gig.  MySQL would still see a 4Gig machine, 
just with lots of memory allocated by the kernel...  In reality that 
"allocated" memory is given back to Xen.

You could then do the same for the other MySQL domU (if they don't initially 
fit in memory at once, suspend the first one to disk).

You should be able to get them both fitting in memory, although you'll 
probably be well advised to configure them both with swap internally ;-)

Have fun; if you do try this please let us know how it goes.  It's such an 
utterly twisted thing to do, I'm very curious to find out if it works!


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