On 08/30/2018 10:54 AM, Eugen Block wrote:
Hi Jay,

You need to set your ram_allocation_ratio nova.CONF option to 1.0 if you're running into OOM issues. This will prevent overcommit of memory on your compute nodes.

I understand that, the overcommitment works quite well most of the time.

It just has been an issue twice when I booted an instance that had been shutdown a while ago. In the meantime there were new instances created on that hypervisor, and this old instance caused the OOM.

I would expect that with a ratio of 1.0 I would experience the same issue, wouldn't I? As far as I understand the scheduler only checks at instance creation, not when booting existing instances. Is that a correct assumption?

To echo what cfriesen said, if you set your allocation ratio to 1.0, the system will not overcommit memory. Shut down instances consume memory from an inventory management perspective. If you don't want any danger of an instance causing an OOM, you must set you ram_allocation_ratio to 1.0.

The scheduler doesn't really have anything to do with this.

Best,
-jay

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