StarCluster supports using Amazon’s Elastic Block Storage (EBS) volumes for persistent storage. These volumes can be anywhere from 1GB to 1TB in size. StarCluster will attach each volume specified in a cluster template to the master node and then share the volume(s) to the rest of the nodes in the cluster via the network file system (NFS). Each volume will be mounted to the path specified by the MOUNT_PATH setting in the volume’s configuration section.
For example, suppose we have the following configuration defined:
[vol myvol] volume_id = vol-v9999999 mount_path = /data [cluster smallcluster] cluster_size=3 keyname=mykey node_instance_type=m1.small node_image_id=ami-8cf913e5 volumes=myvol
In this case, whenever a cluster is launched using the smallcluster template StarCluster will attach the EBS volume vol-v9999999 to the master node on /data and then NFS-share /data to all the nodes in the cluster.
It’s also possible to use multiple EBS volumes by specifying a list of volumes in a cluster template:
Each volume specified in a cluster template must have a unique MOUNT_PATH otherwise an error will be raised.
[vol cancerdata] volume_id = vol-v8888888 mount_path = /data/cancer [vol genomedata] volume_id = vol-v9999999 mount_path = /data/genome [cluster smallcluster] cluster_size=3 keyname=mykey node_instance_type=m1.small node_image_id=ami-8cf913e5 volumes=cancerdata, genomedata
StarCluster’s createvolume command completely automates the process of creating a new EBS volume. This includes launching a host instance in the target zone, attaching the new volume to the host, and formatting the entire volume.
The createvolume command simply formats the entire volume using all of the space on the device rather than creating partitions. This makes it easier to resize the volume and expand the filesystem later on if you run out of disk space.
To create and format a new volume simply specify a volume size in GB and the availability zone to create the volume in:
$ starcluster createvolume --name=my-data 20 us-east-1c
The above command will launch a host instance in the us-east-1c availability zone, create a 20GB volume in us-east-1c, attach the new volume to the host instance, and format the entire volume. The --name option allows you name the volume for easy reference later on when using the listvolumes command or the AWS web console.
If you wish to apply an arbitrary tag to the new volume use the --tag option:
$ starcluster createvolume --tag=mytag 20 us-east-1c
If you want to create a key/value tag:
$ starcluster createvolume --tag mytag=myvalue 20 us-east-1c
You can also use the --bid option to request a spot instance when creating the volume host:
$ starcluster createvolume 20 us-east-1c --bid 0.50
StarCluster does not terminate the host instance after creating a volume. This allows multiple volumes to be created in the same zone using a single host instance. You can pass the --shutdown-volume-host option to the createvolume command to if you’d rather automatically shutdown the volume host after creating the new volume.
Let’s look at an example of creating a 20GB volume in us-east-1c:
$ starcluster createvolume --name=myvol --bid=0.50 20 us-east-1c StarCluster - (http://web.mit.edu/starcluster) Software Tools for Academics and Researchers (STAR) Please submit bug reports to email@example.com >>> No keypair specified, picking one from config... >>> Using keypair: jtriley >>> Creating security group @sc-volumecreator... >>> No instance in group @sc-volumecreator for zone us-east-1c, >>> launching one now. >>> Waiting for volume host to come up... (updating every 30s) >>> Waiting for open spot requests to become active... 1/1 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| 100% >>> Waiting for all nodes to be in a 'running' state... 1/1 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| 100% >>> Waiting for SSH to come up on all nodes... 1/1 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| 100% >>> Checking for required remote commands... >>> Creating 1GB volume in zone us-east-1c >>> New volume id: vol-2f3a5344 >>> Waiting for new volume to become 'available'... >>> Attaching volume vol-2f3a5344 to instance i-fb9ceb95... >>> Formatting volume... mke2fs 1.41.11 (14-Mar-2010) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=0 blocks, Stripe width=0 blocks 65536 inodes, 262144 blocks 13107 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=268435456 8 block groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376 Writing inode tables: done Creating journal (8192 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 30 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override. >>> Leaving volume vol-2f3a5344 attached to instance i-fb9ceb95 >>> Not terminating host instance i-fb9ceb95 *** WARNING - There are still volume hosts running: i-fb9ceb95 *** WARNING - Run 'starcluster terminate volumecreator' to terminate *** WARNING - *all* volume host instances once they're no longer needed >>> Creating volume took 7.396 mins >>> Your new 1GB volume vol-2f3a5344 has been created successfully
In the above example we name the volume myvol and use a spot instance for the volume host. Notice the warning at the bottom of the above output. StarCluster will leave the host instance running with the new volume attached after creating and formatting the new volume. This allows multiple volumes to be created in a given availability zone without launching a new instance for each volume. To see the volume hosts simply run the listclusters command:
$ starcluster listclusters volumecreator StarCluster - (http://web.mit.edu/starcluster) Software Tools for Academics and Researchers (STAR) Please submit bug reports to firstname.lastname@example.org ------------------------------------------------- volumecreator (security group: @sc-volumecreator) ------------------------------------------------- Launch time: 2011-06-13 13:51:25 Uptime: 00:02:09 Zone: us-east-1c Keypair: mykey EBS volumes: N/A Cluster nodes: volhost-us-east-1c running i-fd9clb9z (spot sir-2a8zb4lr) Total nodes: 1
From the above example we see that we have a volume-host in us-east-1c called volhost-us-east-1c. Any volumes that were created will still be attached to the volume host until you terminate the volumecreator cluster. If you’d rather detach the volume after it’s been successfully created use the --detach-volume (-d) option:
$ starcluster createvolume --detach-volume 20 us-east-1c
You can login to a volume host instance using:
$ starcluster sshnode volumecreator volhost-us-east-1c
After logging in you can inspect the volume, upload data, etc. When you’re done using the volumecreator cluster don’t forget to terminate it:
$ starcluster terminate volumecreator
If you’d rather avoid having to terminate the volumecreator each time you can pass the --shutdown-volume-host (-s) option to the createvolume command to have StarCluster automatically terminate the host-instance after successfully creating the new volume:
$ starcluster createvolume --shutdown-volume-host 20 us-east-1c
In addition to creating and formatting new EBS volumes StarCluster also allows you to browse and remove your EBS volumes.
To get a list of all your volumes as well as their current status use the listvolumes command:
$ starcluster listvolumes StarCluster - (http://web.mit.edu/starcluster) Software Tools for Academics and Researchers (STAR) Please submit bug reports to email@example.com volume_id: vol-be279s08 size: 5GB status: available availability_zone: us-east-1d create_time: 2011-10-22 16:18:57 Total: 1
To list details for a single volume by name use the --name (-n) option:
$ starcluster listvolumes --name my-big-data
To list details for a single volume by id use the --volume-id (-v):
$ starcluster listvolumes -v vol-99999999
If you’d like to see details for all volumes with a given tag use the --tag (-t) option:
$ starcluster listvolumes -t my-big-data $ starcluster listvolumes -t mytag=myvalue
You can also filter the volumes by status using the --status (-S) flag:
$ starcluster listvolumes -S available
and by volume size (in GB) using the --size (-s) option:
$ starcluster listvolumes -s 20
and also by attachment state using the --attach-status (-a) option:
$ starcluster listvolumes -a attached
Other filters are available, have a look at the help menu for more details:
$ starcluster listvolumes --help
This process cannot be reversed!
To permanently remove an EBS volume use the removevolume command:
$ starcluster removevolume vol-99999999
After you’ve created and used an EBS volume over time you may find that you need to add additional disk space to the EBS volume. Normally you would need to snapshot the volume, create a new, larger, volume from the snapshot, attach the new volume to an instance, and expand the filesystem to fit the new volume. Fortunately, StarCluster’s resizevolume command streamlines this process for you.
The EBS volume must either be unpartitioned or contain only a single partition. Any other configuration will be aborted.
For example, to resize a 10GB volume, say vol-99999999, to 20GB:
$ starcluster resizevolume vol-99999999 20
The above command will create a new, larger, 20GB volume containing the data from the original volume vol-99999999. The new volume’s filesystem will also be expanded to fit the new volume size.
Just like the createvolume command, the resizevolume command will also launch a host instance in order to attach the new volume and expand the volume’s filesystem. Similarly, if you wish to shutdown the host instance automatically after the new resized volume has been created, use the --shutdown-volume-host option:
$ starcluster resizevolume --shutdown-volume-host vol-99999999 20
Otherwise, you will need to terminate the volume host manually after the resizevolume command completes.
In some cases you may need to replicate a given volume to another availability zone so that the data can be used with instances in a different data center. The resizevolume command supports creating a newly expanded volume within an alternate availability zone via the --zone (-z), flag:
$ starcluster resizevolume -z us-east-1d vol-9999999 20
The above command will create a new 20GB volume in us-east-1d containing the data in vol-99999999. If you only want to move the volume data without resizing simply specify the same size as the original volume.