Working with block storage

To add persistent storage to your cloud environments, you would use block storage devices, namely volumes and volume snapshots. A volume is attached to an instance and mounted as a file system for use by an application. A volume snapshot is a point-in-time snapshot of a volume that can be shared with other cloud users. Before a snapshot can be used, it is necessary to create a volume from it.

Volume storage

Operations, such as creating a new volume and listing the existing ones, are performed via the VolumeService. To start, let’s create a 1GB volume.

vol = provider.block_store.volumes.create('CloudBridge-vol', 1, 'us-east-1e')

Next, let’s attach the volume to a running instance as device /dev/sdh:

vol.attach('i-dbf37022', '/dev/sdh')
# 'in-use'

Once attached, from within the instance, it is necessary to create a file system on the new volume and mount it.

Once you wish to detach a volume from an instance, it is necessary to unmount the file system from within the instance and detach it. The volume can then be attached to a different instance with all the data on it preserved.

# 'available'

Snapshot storage

A volume snapshot it created from an existing volume. Note that it may take a long time for a snapshot to become ready, particularly on AWS.

snap = vol.create_snapshot('cloudbridge-snap',
                           'A demo snapshot created via CloudBridge.')
# 'available'

In order to make use of a snapshot, it is necessary to create a volume from it:

vol = provider.block_store.volumes.create(
    'CloudBridge-snap-vol', 1, 'us-east-1e', snapshot=snap)

The newly created volume behaves just like any other volume and can be attached to an instance for use.