Elastic Block Store: In Depth

Amazon EC2 (aws-ec2) and compatible apis such as Eucalyptus (eucalyptus) include support for remountable block devices, called EBS. In jclouds, control features for this are exposed in 3 ways: hooks within ComputeService (EC2TemplateOptions and viewing via NodeMetadata), directly through the provider api (ElasticBlockStoreClient), and our clojure functions (ebs2.clj).

ComputeService Integration

jclouds reports current status of volume mappings inside a Node’s Hardware field. You can setup volume mappings with extended template options.

Viewing the current volumes attached to a node

EBS volumes will report in the collection returned by node.getHardware().getVolumes() as type Volume.Type.SAN

Setting up Volume Mappings

jclouds also has a means to setup volume mappings when you start your nodes. Here’s an example:

template.getOptions().as(EC2TemplateOptions.class)
        // .unmapDeviceNamed("/dev/foo)
        .mapEphemeralDeviceToDeviceName("/dev/sdm", "ephemeral0")
        .mapNewVolumeToDeviceName("/dev/sdn", volumeSize, true)
        .mapEBSSnapshotToDeviceName("/dev/sdo", snapshot.getId(), volumeSize, true);

Elastic Block Store Client

Getting access to the client

ElasticBlockStoreClient ebsClient = EC2Client.class.cast(context.getProviderSpecificContext().getApi())
        .getElasticBlockStoreServices();

Generating a snapshot

Snapshot snapshot = ebsClient.createSnapshotInRegion(volume.getRegion(), volume.getId());

ebs2.clj

(use 'org.jclouds.ec2.ebs2)

(def ec2 (compute-service "aws-ec2" "ACCESSKEY" "SECRETKEY" :sshj))

(volumes ec2)