[TriLUG] Memcached and VMware ESX

John Wheeler jwheeler at etherealfringe.com
Thu Jul 2 12:04:29 EDT 2009

Hey guys,

I'm re-factoring some caching code for our web application and working  
with IT to implement our new dedicated memcached servers.
We have two machines with 32Gb a piece.

The nature of our application is that multiple client communities  
receive the same kind of service but with completely different data  
sets and search vectors.
We want to balance the load by distributing the heavy lifting of some  
search vectors to memcahce.

We can either install thin OS's on each machine and have two memcached  
servers, or we can lose 4Gb off the top on each box (to the VMware  
hypervisor) and create virtual memcached servers.
We run WMware ESX.

The key is that this has to be as fast as possible.
I am looking for opinions on whether or not running inside the  
hypervisor will slow the speed of direct memory access by the  
memcached processes living inside the virtual machines by any  
significant amount relative to normal memcached response times.
The benefit we get by virtualizing is the ability to provision  
memcached server pools for individual client implementations, keeping  
heavier application deployments bucketed into their own pools so as  
not to overwhelm and push out the smaller, less accessed  
implementation's cache entries.

I am not really concerned about losing the 4Gb to the hypervisor, but  
should running in a virtualized environment like this slow down our  
application requests to the memcached server?

John Wheeler
Web Applications Developer
jwheeler at etherealfringe.com

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