Block Storage Volumes on Rackspace Cloud

Volumes are a component of OpenStack that handle persistent data storage. Volumes are block-level storage devices that can be attached to instances. They behave like hard drives for virtual machines and can be detached and reattached to different instances. You can also boot VMs from volumes if they are bootable and outfitted with an OS from an image. For example, if your instance needs additional storage beyond what’s available on the root disk, you would create a volume and attach it to your instance.

NOTE: All volumes make use of multi-pathing, which helps to maintain high-availability in the event of networking issues on the infrastructure.

Data Source Types

Volumes can be built from three possible sources. These sources dictate what will be on the volume once it's finished creating.

• Blank Volume - This is a blank volume, useful for acting as a storage repository attached to an instance.
• Image - This is a volume that will contain an operating system from a chosen image. Usually these are built to be the boot source for an instance.
• Volume Snapshot - A snapshot of another storage volume. Useful for cloning a volume.

Types

Note: LUKS encryption, which stands for "Linux Unified Key Setup," is a disk encryption standard primarily used on Linux systems that allows users to encrypt entire partitions or hard drives by requiring a passphrase to access the data. While "encryption at rest" refers to any method of encrypting data while it's not actively being used (like on a hard drive), LUKS is a specific, widely used implementation of this concept primarily within the Linux ecosystem

• Capacity: Large-capacity storage with LUKS encryption. Best for workloads that require large volumes but may not need high-speed performance.
• Performance: High-performance storage with LUKS encryption. Suitable for workloads that require high I/O demands like databases, virtual machines with heavy workloads, and data-intensive applications.
• Standard: Standard storage with LUKS encryption. Standard Storage works well for general-purpose data storage, backups, and applications that don't require high performance.
• HA-Standard: High-availability standard block storage with at-rest encryption. Designed for workloads requiring redundancy and failover capabilities. The HA component refers to a redundant block storage system designed to maintain data availability in case of hardware failures.
• HA-Performance: High-availability block storage optimized for performance, with at-rest encryption. This is the best choice for mission-critical applications that need both speed and HA. The HA component refers to a redundant block storage system designed to maintain data availability in case of hardware failures.

Volume Actions

There are a variety of actions you can take on a Storage Volume. Be aware that some actions are only available when the volume is not attached to a server. Below is a list of the actions and what they do.

Data Protection

⚠ IMPORTANT: When creating a snapshot, backup, or cloning a volume it is best practice to freeze filesystem or stop the VM the volume is attached to. Taking these precautions will greatly decrease the risk of inconsistency or corruption on the copied data.

• Create Snapshot - A fast, point-in-time copy of a volume stored on the same backend, mainly used for quick rollback or cloning and dependent on the original volume.
• Create Backup - A full, independent copy of a volume’s data stored in a separate backup backend, intended for long-term retention and disaster recovery.
• Create Image - The Volume must be in an Available state, not attached to a VM. If the volume is bootable, this allows you to create an image that you can spin servers up from.
• Clone Volume - Creates a new Volume copied from an existing one.
• Restore from Snapshot - The Volume must be in an Available state, not attached to a VM. If you have a snapshot, you can revert to the snapshot's point in time.

Instance Related

• Bootable - Make the volume a bootable volume, allowing you to choose it as the boot source for a VM. Bear in mind that this will only work if the volume is properly configured to be an operating system disk.
• Attach/Detach - Attaches or Detaches your volume from a server. While it's generally possible to detach a volume from a VM before unmounting it within the OS, it is advisable to unmount it first.

Capacity & Type

NOTE: Your project's quota limitations may prevent you from scaling or creating new volumes. Be sure to check you have the necessary quota space and request an increase via ticket if you feel you need more.

• Extend Volume - Extends the size of the volume to a larger size. Be aware that if the volume is already mounted within a VM's filesystem, it will likely not automatically show the extended size within the OS. You may still need to extend the partition using the methods appropriate for your VM's operating system.
• Change Type - Changes the type of the volume. For example converting a Performance volume to an HA-Performance volume. It is highly advisable to perform this action when the volume is in an Available state.

• Create Transfer - Available on the HA Volume types. This allows you to transfer a volume from one project to another.
• Delete - Deletes the volume. You should detach the volume prior to issuing a delete.

Using Your Volume

After you've attached your Cloud Block Storage volume to your server, you'll be able to see it within the OS as un unformatted attached partition. You'll need to then use the appropriate steps to prepare, format, and mount the volume as a new drive for your server to use.

Additional Documentation

OpenStack Cinder Documenation