Comment 2 for bug 1920886

The following is an actual example. Referring to the nova documentation [1], the subdirectory_name is set to split the image cache directory for each node. Please note that the entire /opt/stack/data/nova/instances/ is shared.

I know this is a strange use case. I found this issue through trial and error while verifying live migration.

$ grep subdirectory_name /etc/nova/nova-cpu.conf
subdirectory_name = _base_$my_ip

$ find /opt/stack/data/nova/instances/
/opt/stack/data/nova/instances/
/opt/stack/data/nova/instances/locks
/opt/stack/data/nova/instances/locks/nova-storage-registry-lock
/opt/stack/data/nova/instances/locks/nova-1da480fd0bd6d365cce06421659d922b1bbed441
/opt/stack/data/nova/instances/compute_nodes
/opt/stack/data/nova/instances/22a86da9-f6db-493d-aca7-3fcdc2d318a8
/opt/stack/data/nova/instances/22a86da9-f6db-493d-aca7-3fcdc2d318a8/disk.info
/opt/stack/data/nova/instances/22a86da9-f6db-493d-aca7-3fcdc2d318a8/disk
/opt/stack/data/nova/instances/22a86da9-f6db-493d-aca7-3fcdc2d318a8/console.log
/opt/stack/data/nova/instances/_base_192.168.0.1 # for node1
/opt/stack/data/nova/instances/_base_192.168.0.1/1da480fd0bd6d365cce06421659d922b1bbed441
/opt/stack/data/nova/instances/_base_192.168.0.2 # for node2
/opt/stack/data/nova/instances/_base_192.168.0.2/1da480fd0bd6d365cce06421659d922b1bbed441

[1] https://github.com/openstack/nova/blob/3de7fb7c327db348d04d15d4cd3c4f811a336126/nova/conf/imagecache.py#L57