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NathanH (4) [Avatar] Offline
#1
Just a heads up. I ran into a ceiling starting up additional VM's today. The issue turned out to be all the RAM on the host was allocated to other VM's. Stopping those VM's did not aliviate the issue, but deleting a VM to free up enough RAM did. Some digging shows that overcommitment is possible, but disabled by default.

http://www.sebastien-han.fr/blog/2012/09/22/openstack-memory-overcommit/

You might want to consider mentioning this in chapter 2, or use smaller flavors. Running 4 GB instances will eat up most of the resources that most test system will have quickly. smilie
cody.bumgardner (57) [Avatar] Offline
#2
Re: RAM overcommitment
Hi NathanH,

Thanks for the info. At least for the OpenStack trunk they claim a default oversubscription of 1.5 on RAM. I will have to check and see if this is the case.

See Oversubscription:
http://docs.openstack.org/trunk/openstack-ops/content/compute_nodes.html

Good idea on the node sizes. I expect most can get away with micro for testing.

Thanks,
Cody