[Openstack-operators] Hypervisor free memory recommendations

Tim Bell Tim.Bell at cern.ch
Thu Sep 4 17:28:14 UTC 2014

We found the default (512MB) too small for our RHEL based KVM hypervisors with our local monitoring and puppet running. Some space for file logs etc. is also good.

The annoying thing on setting this value higher was that we then found packing problems. Since we allocate on memory, a 48GB machine with 1GB reserved only has enough memory for 23 2GB instances. However, you can’t buy 50GB machines so we just had to make do ☺


From: Juan José Pavlik Salles [mailto:jjpavlik at gmail.com]
Sent: 04 September 2014 18:46
To: Tomasz Napierala
Cc: openstack-operators at lists.openstack.org
Subject: Re: [Openstack-operators] Hypervisor free memory recommendations

Hi Tomasz, thanks for your answer. I'll start with 10% and see what happens. Thanks again!

2014-09-04 13:37 GMT-03:00 Tomasz Napierala <tnapierala at mirantis.com<mailto:tnapierala at mirantis.com>>:

On 04 Sep 2014, at 18:04, Juan José Pavlik Salles <jjpavlik at gmail.com<mailto:jjpavlik at gmail.com>> wrote:

> Hi guys, I'm running a Grizzly cloud with Ubuntu 12.04+KVM. I'd like to know if there's any kind of recommended free RAM for the Hypervisor. I know there's a nova variable called "
> reserved_host_memory_mb" but don't know what a proper value would be.
Check on deployed compute node that has no running VMs, add some margin, say 10% and you should be fine. Usually compute nodes are not consuming extra memory besides VMs.

Tomasz 'Zen' Napierala
Sr. OpenStack Engineer
tnapierala at mirantis.com<mailto:tnapierala at mirantis.com>

Pavlik Salles Juan José
Blog - http://viviendolared.blogspot.com
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