Cloned from launchpad blueprint https://blueprints.launchpad.net/nova/+spec/nova-instance-storage-loadbalancing.

Description:

The default path of instance location is in /var/lib/nova/instances/#InstanceID'/

If you want LiveMigrations you are advised to have this directory on a centralized storage, for example on NFS - as explained here: http://docs.openstack.org/trunk/openstack-compute/admin/content/configuring-live-migrations.html

There might be good reasons for having more than 1 instance directory for VM deployments - for example:
- In a big lanscape you might want to have more than 1 central storage mounts, i.e. 2 NFS mounts
- In compute-nodes with multiple local raid arrays you want to distribute instances over all arrays

If you want to use more than 1 location you need:
- more directories below /var/lib/nova/instances/ with UniqueIDs
- a patch for Openstack to deploy on the directory with the least utilization

Even better would be to have a modular scheduler integrated so that it would be flexible on which algorithm the scheduler chooses the instance directories - f.e. one target for high IO VMs etc ... 

--> I already have a working implementation for scheduling instances over 2 directories based on utilization which I could commit.



Specification URL (additional information):

None