Volumes

Volumes

Volumes represent block storage. Conceptually, storage devices can be used to store data in a persistent manner in the cloud.

Overview

Cloud storage is fast, reliable, and portable. Volumes can be newly created or created from snapshots.

The ability to create volumes is dependent on the support for volumes enabled by the underlying cloud provider. At the time of this writing, volume support is only available in the Amazon cloud.

Creating Volumes

To create a new volume, navigate to Infrastructure > Volumes. If volumes had been previously created either within enStratus or via the cloud provider, they will be listed in the volumes table. Select +create_volume and complete the resulting dialog box.

The name of the volume is a logical name that will be used within enStratus to reference the volume. The size of the volume is should be between 1 and 1000 gigabytes (1 Tb).

The Zone in which a volume is created is important because volumes may only be attached to servers in the same zone. Billing code and group complete the creation options for a volume.

Volume creation takes only a few minutes to complete. Once the volume is created it will be added to the list of volumes. Since newly created volumes are not attached to a server, the Device and Current Server columns will be blank.

Attaching Volumes

Volumes and servers must share an availability zone for volume attachment to succeed. Volumes are attached as block storage devices and are neither partitioned nor formatted when attached. enStratus allows for automated attachment, formatting, and mounting of new volumes only when starting a new server.

To attach a volume to a server, select the volume for attachment and select the green actions button. The only required information to attach a volume is the name of the server to which the volume will be attached. The list of servers that share an availability zone will populate the dropdown selector.

Optionally, a device name may be selected for the volume. In this case, I have chosen a device name of sdh, which means the device will appear as /dev/sdh on the server:

p335@ApplicationServer:~$ sudo fdisk -l

Disk /dev/sdh: 2147 MB, 2147483648 bytes 255 heads, 63 sectors/track, 261 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000

Disk /dev/sdh doesn't contain a valid partition table

Once the volume is attached, it can be considered and treated somewhat like an external hard drive attached to the server. Standard hard drive activities are available including partitioning, formatting, and mounting.

Creating Snapshots

Snapshots are created from volumes and volumes are created from snapshots.

A snapshot of a volume represents a differential backup of the data contained on the volume. This means that only the blocks that have changed are saved each time a snapshot is created. To create a snapshot, select the green actions button for the volume, and choose make_snapshot. The only required information to create the snapshot is a logical name for the snapshot. Once the snapshot is saved, the snapshot will appear in the snapshots page in the enStratus console.

Deleting Volumes

To delete a volume, click on the green action button associated with the volume and choose delete. A dialog box will prompt you to confirm the action and the volume will be removed from the volumes list.

Volume Strategies

Volume storage is persistent beyond the life of the server to which it was attached. This makes volumes a very useful item for managing data storage in the cloud. In a high-availability failure-tolerant automated environment, enStratus leverages volumes to restore applications to an operational state without data loss.
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