Does a VM instance own multiple compute nodes' CPU ability?

asked 2013-10-07 04:12:50 -0600

Andy gravatar image

updated 2013-10-08 01:42:47 -0600

If I have three compute nodes in my system, Can I create a VM instance which owns the three compute nodes' CPU ability? or a VM just can have one compute node's CPU ability?

Same concept question for Cinder, if I have three storage nodes(cinder), each node has 100 GB storage. Can a user create a 300 GB volume, or a user just can create a 100 GB volume at a time?



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answered 2014-12-30 04:50:43 -0600

Regarding VMs, No you can't. When you try to launch a VM the scheduler selects any ONE available compute node and launch the instance in that node. If you try to launch any flavor which any compute node could not hold, the you will get a 'No valid host found' error.

Regarding Cinder, if the cinder backend is ceph, then you can create a combined volume. If you are using local disks, then it works on the same concept of LVM and volumes from other cinder nodes cant be used to create a volume-group.

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answered 2014-12-31 03:17:18 -0600

foexle gravatar image

Yes and no :) as the post above mentioned you, an instance is running only on one compute node but you can over provisioning your comp nodes with ratio (cpu and ram) settings. You can spawn an instance with the resource of 3 compute nodes theoretically but you can't use the real ressources. You'r instance is only running on one node and you don't have the possibility to combine the processing power to one instance over all compute nodes (not with OpenStack features).

Cheers Heiko

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Asked: 2013-10-07 04:12:50 -0600

Seen: 941 times

Last updated: Dec 31 '14