Create a Clone of a Cloud Block Storage Volume

A clone of a Cloud Block Storage (CBS) volume is a copy made of an existing volume at a specific moment in time. At a high-level, the volume cloning process does the following:

  • Creates a Logical Volume Management (LVM) copy on the write segment of your existing volume.
  • Creates a new blank volume on a separate storage node.
  • Directly transfers the volume data from the existing volume to the new volume.

The end result is an identical CBS volume that you can immediately attach and use. You have the option to change the volume type before beginning the volume clone process. Additionally, volume cloning also allows you to increase the size of the new volume. The cloned volume must be the same size or larger than the original volume. Keep in mind, if you do use cloning to increase the size of your volume, be sure to resize your file system (if supported) to take advantage of the new, larger clone.

Before the volume cloning feature became available, customers were encouraged to use volume snapshots when they needed a copy of a volume. The advantage to using volume cloning instead of snapshotting is that volume cloning transfers your data directly between volumes, without the need to use a Cloud Files snapshot as an intermediate step.

Volume cloning shares many similarities with volume snapshots. For example, they both use LVM as the primary copy and locking mechanism, and therefore, you should detach the volume before cloning.

Create a Volume Clone

It is a good idea to detach your volume from your server before you take a volume clone. This is the safest method to prevent your server from writing information while you are backing it up. That could get your data out of sync and could create a problem. To detach your volume, see Detach and delete Cloud Block Storage volumes. You can always re-attach the volume by following the attach steps in Create and attach a Cloud Block Storage volume.

More advanced users might sync the file system to ensure the integrity of the data on your snapshots. Performing a sync flushes file system buffers and writes the data out to disk. If you are unfamiliar with syncing your file system, consider detaching your volume before snap shotting.

Steps to Create a Volume Clone

  1. Log in to the Cloud Control Panel.

  2. Navigate to Rackspace Cloud -> Storage -> Block Storage Volumes and click on your volume.

  3. Click Actions on the Volume Details screen to open the Clone Volume pop-up window.

  4. Click the Clone Volume link.

  5. Give the new volume a name. The default is the volume's name followed by the -clone suffix.

  6. Specify the volume type and size.

  7. Click Clone Volume.

  8. After the new volume details page displays, you can safely reattach your volume.

Delete a Volume Clone

  1. After you create a cloned volume, you can treat it like any other existing volume.

  2. You can delete a CBS volume by clicking Delete Volume from Actions on the Volume Details screen.

Frequently Asked Questions About Volume Cloning

How is cloning different from using a snapshot?

You cannot use a snapshot directly as a volume. You need to create a volume from the snapshot before you can attach it to your server. Snapshots are stored redundantly in Cloud Files. However, creating volumes from snapshots is a slower process than creating a volume from a clone. If your application is time sensitive, consider using volume cloning instead. A volume clone is usable copy of the source volume and you can attach and use it immediately.

Do I need to detach my volume before cloning?

While not required, it is a good idea to detach your volume from your server before you create a clone. This safe method prevents your server from writing data to the volume during clone creation and avoids a situation of inconsistent data between a cloned volume and its source volume. If you choose to leave your source volume attached before creating a clone, you need to both sync current buffers and prevent future writes during the actual clone operation. More advanced users might choose to freeze or sync their file system before creating a volume clone. Performing a sync flushes file system buffers and writes the data out to disk.

If you are unfamiliar with syncing your file system, consider detaching your volume before snapshotting. The volume cloning process works similar to creating a volume snapshot through the Application Programmer Interface (API). Note that as soon as the initial clone operation returns a `200` response, the local point-in-time snapshot of your volume is ready, and you can continue using the original volume. The cloned volume remains in *creating* status until the source volume data has been fully copied to the new clone.

Can I create multiple clones from a single volume simultaneously?

No. Creating multiple clones simultaneously from the same volume will fail.

Can I clone between regions?

No. You can clone volumes only within the same region.

Can I simultaneously snapshot and clone the same volume?

No. Volume snapshots and cloning share the same locking mechanism and therefore cannot happen simultaneously on the same volume.

Volume Cloning Constraints

You cannot create more than one clone per volume at a time. Snapshots and cloning use the same locking mechanism, so a snapshot and clone of the same volume cannot run concurrently.