https://docs.rackspace.com/support/how-to/prepare-your-cloud-block-storage-volume about support-how-to HOT 1 OPEN

Doc troubleshoot-a-cloud-block-storage-volume-in-read-only-mode would also need the _netdev reference removed. The fstab examples should also have the option removed.

To be clear while the lines that appear in the docs aren't factually incorrect, they are irrelevant and not needed for CBS (and cause issues for NFS as stated above).

This line includes the _netdev option, which prevents attempts to mount the volume until all networking is running.

Note: In your fstab options, add the _netdev option. This option prevents attempts to mount the volume until all networking is running.

From the Cloud Server perspective, these block devices are available from the get go - they aren't network mounted and do not make any use of the cloud servers network. (it's the underlying hypervisor that relies on the network for the CBS to mount).

Delaying their mount until the Cloud Servers OS is running is pointless.

from support-how-to.