OpenStack Compute (nova)

CPU and Instance Limit

Asked by Peter Borghard

All,

I have a question about the number of instances that can be created based on the compute nodes available cpu/memory . Is there any over provisioning? Or will the compute node stop adding instances once the memory or cpu limit has been reached.

Thanks,
Peter Borghard

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Elvinas Piliponis (elvinas-piliponis) said : 		#1

It seems that memory cannot be overprovisioned. At least on OpenStack layer as KVM itself can overprovision without any problems.
CPU can be overprovisioned by setting "max_cores=N" in nova.conf on compute node to the number you want.

But in any case Mem/CPU counters are the hard limits and as soon as they are reached, new instance creation will fail. At least this is what happens with SimpleScheduler.

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Zhaoyi Luo (zhaoyi-luo) said : 		#2

This doc may help you: http://docs.openstack.org/trunk/openstack-compute/admin/content/ramfilter.html
I didn't try it.

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