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

To: "'Ernst Bachmann'" <e.bachmann@xxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: AW: [Xen-users] Use hard drive as physical mem for xen vm
From: "Oliver Neumann [New Identity AG]" <oliver.neumann@xxxxxxxxxxxxxx>
Date: Fri, 11 Nov 2005 15:15:48 +0100
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>> I've got a machine that should serve 2 XenUs as mysql cluster nodes with
>> realy big memory consumption. As mysql cluster will need approx. 4GB memory
>> on each XenU, I wondered if I could use hard disc space as memory for the
>> XenU that appears as real physical memory within the VM. Swap is no
>> alternative as mysql cluster nodes check the physical memory and if that is
>> not enough, they will not work.
>> How can I do that?

>Invest a few extra € and put 8Gigs of ram in that server?
>Reconfigure the mysql instances to run with just 2GB?
>Seriously, mysql wants physical ram there for a reason, if that memory is 
>swapped, it would be faster for mysql to just read the blocks from its db 

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: 
is irrelevant, the cluster does not need to be fast (it actually can be damn 

Unfortunately there seems to be no chance to save the money using Xen with 
emulated physical RAM, right?

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