On Mon, 9 May 2011, David Boreham wrote:
On 5/9/2011 6:32 PM, Craig James wrote:
Maybe this is a dumb question, but why do you care? If you have 1TB RAM
and just a little more actual disk space, it seems like your database will
always be cached in memory anyway. If you "eliminate the cach effect,"
won't the benchmark actually give you the wrong real-life results?
The time it takes to populate the cache from a cold start might be important.
you may also have other processes that will be contending with the disk
buffers for memory (for that matter, postgres may use a significant amount
of that memory as it's producing it's results)
David Lang
Also, if it were me, I'd be wanting to check for weird performance behavior
at this memory scale.
I've seen cases in the past where the VM subsystem went bananas because the
designers
and testers of its algorithms never considered the physical memory size we
deployed.
How many times was the kernel tested with this much memory, for example ?
(never??)
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