= Persistent storage =

/!\ Unfortunately, per Bug #1334956, the storage and block-storage-broker
    charms are not yet available in the charm store for trusty so
    this documentation does not work as written.

The cassandra charm takes advantage of the storage subordinate charm
and the block-storage-broker charm. With these two charms cassandra can
either request new volumes are created or use existing volumes.

For requesting new volume creation, just set external_volume_mount in
the cassandra charm and root, provider and volume_size for the storage
subordinate charm.

If using existing volumes, also set the volume_map for the storage
subordinate charm.


Example using existing volumes:

juju deploy -n 3 cassandra
juju set cassandra external_volume_mount="/srv/data"

juju deploy storage
juju set storage 
        root=/srv/data
        provider=block-storage-broker
        volume_size=10
        # Volume map needed for existing storage
        volume_map="{cassandra/0: e09be717-384b-43e3-b06a-3a68b5a2252d,
                     cassandra/1: ebd35228-6972-4e22-86a8-37483581154a,
                     cassandra/2: 9f02b67b-72da-4e22-98ee-10a95c1b298d}"

juju deploy block-storage-broker

juju add-relation storage cassandra
juju add-relation storage block-storage-broker


See the READMEs for the storage subordinate charm and the
block-storage-broker charm for more detail on persistent storage.