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

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Re: Use hard drive as physical mem for xen vm
From: Charles Duffy <cduffy@xxxxxxxxxxx>
Date: Fri, 11 Nov 2005 11:33:13 -0600
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If you want to force MySQL to use swap in place of physical memory, why not just find the place in the source where it checks for physical (vs virtual) memory and modify it to require only that adequate virtual memory be available?

Using virtual memory without the knowledge of the underlying OS is just a really, really, really bad idea. In-memory pages get rewritten *exceedingly* frequently in a great many cases -- unlike pages which the OS intelligently chooses to swap out, which are selected *because they're not frequently used*. If you're doing this behind the OS's back -- just mapping a big region of "physical memory" to disk -- then you no longer have any of those algorithms working in your favor, and the wait times will be *huge*.

As the other respondants have suggested -- don't do it this way. Modify MySQL instead.

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