[Openstack-operators] Hypervisor free memory recommendations

Jay Pipes jaypipes at gmail.com
Thu Sep 4 18:18:57 UTC 2014

On 09/04/2014 01:51 PM, Juan José Pavlik Salles wrote:
> Hi Jay, I do agree about 10% being too much memory in big nodes, but
> right now we are using small ones (too small if you ask). These new
> nodes are 16GB so if I reserve 4 Gb for the dom0 I'd be loosing 25% of
> the available RAM. I was thinking about something like: if you have got
> less than 32GB give 10% of it to the dom0 and If you have got more than
> 32GB go with 4GB for the dom0. Maybe different environments will need
> different rules, but this should work in most standar deployments I'd
> say. Jay, you mentioned that big nodes running many VMs don't neet more
> than 4GB of dedicated RAM, haven't you ever had any swapping situation
> in that kind of scenarios?

One more thing of note... if you have a lot of custom host or IDS 
monitoring or custom host applications running, you may want to increase 
the host RAM. By "custom" I mean anything other than 
Nagios/Zabbix/Ganglia-type stuff, which tend to be pretty low-memory 

Do some investigation of a sample packed and sparse compute node and 
adjust as you see fit.


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