Qubes OS R3.2 introduced the concept of storage drivers and pools. This feature was a first step towards a saner storage API, which is heavily rewritten in R4. See here for documentation on storage pools in R4.
A storage driver provides a way to store VM images in a Qubes OS system.
Currently, the default driver is
xen which is the default way of storing
volume images as files in a directory tree like
A storage pool driver can be identified either by the driver name with the
driver key or by the class name like this:
class=qubes.storage.xen.XenStorage. Because R3.2 doesn’t use Python
setup_hooks, to actually use a short driver name for a custom storage driver,
you have to patch
qubes-core-admin. You can use the
class config key
instead, when your class is accessible by
import in Python.
A pool (in R3.2) is configuration information which can be referenced when
creating a new VM. Each pool is saved in
storage.conf. It has a name, a
storage driver and some driver specific configuration attached.
When installed, the system has, as you can see from the contents of
/etc/qubes/storage.conf, a pool named
default. It uses the driver
default pool is special in R3.2. It will add
configuration value from
defaults[pool_config], if not overwritten.
Currently the only supported driver out of the box is
xen. The benefit of
pools (besides that you can write your own storage driver e.g. for Btrfs) in R3.2
is that you can store your domains in multiple places.
You can add a pool to
storage.conf like this:
[foo] driver=xen dir_path=/opt/qubes-vm
Now, when creating a new VM on the command-line, you may pass the
qvm-create to have the VM images stored in pool
foo. See also
While the current API is not as clean and beautiful as the R4 API, it allows you to write your own storage drivers e.g. for Btrfs today.