Volume over usage or nova availability zone

OpenStack gives us possibility to avoid nova-scheduler service while boot VMs.
This possibility has a name availability zone, and it is very strong, magical:)
Just providing --availability-zone=nova:host_name you can boot VM on a preferred host.
For example,

nova boot --image 123456 --flavor 2 --availability-zone nova:compute-0-8

will boot VM on host compute-0-8.
But every magic has a backside. If you will use such an option not wisely you can receive disk over usage problem, like this:



Summary: You can avoid nova-scheduler by passing --availability-zone nova:host_name, but be careful because no disk filters will be used in this case (nova-scheduler applies filters to find out on which of computes is enough space to boot VM).

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