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Intentionally "freezing" a state

Create a snapshot of your volume before undertaking any – potentially risky – change. If things do not work as you would like them to after the change (and if a specific repair is not an option), you can revert the volume to the snapshot, i.e. restore the content of the volume to where it was before the change. A volume snapshot is a momentary image of a volume as a whole (including all programs and data, as well as boot loader, partitioning, etc.) with the bytes exactly as they are on the virtual hard drive.

It goes without saying that snapshots are not only useful when the horse has already bolted. When testing changes on a lab setup before their productive deployment, you can use snapshots to run through the process as many times as you would like in order to optimize e.g. scripts or other parameters.

All it takes to create a snapshot is a simple HTTPS request to our API, e.g.:

curl -i -H "Authorization: Bearer YourApiTokenGoesHere" -F name="pre-dist-upgrade" -F source_volume="2db69ba3-1864-4608-853a-0771b6885a3a" https://api.cloudscale.ch/v1/volume-snapshots

As always, you will find all the supported requests and attributes in our detailed API documentation.

Technical details and tips

Snapshots are crash-consistent: if you created a snapshot at a time point X and now revert the volume to the snapshot (e.g. after a failed software upgrade), the server will behave as if the volume was unplugged at time point X and only plugged back in again now. Write caches and other data that were not on the volume at time point X cannot be restored in this way. It is probably worth clarifying if and how your setup can handle a state of this kind. It may be advisable to stop tricky services before creating a snapshot, to do a sync, or to shut down the server completely.

In the case of more than one volume, please also note that although volume snapshots are individually crash-consistent, the datasets do not relate to exactly the same time point when two or more volumes are snapshotted during live operations. In order to avoid differences here, create the snapshots when the server is shut down.

By the way, if you have upscaled the volume since creating a snapshot and then return to the snapshot, the volume will automatically be reduced to the size it was when the snapshot was created.

Ultimately, deleting volumes is only possible when there are no more snapshots of them. If a snapshot is still available for a root volume, the corresponding server cannot be deleted either. Therefore, if required, delete any snapshots before you delete volumes or servers.

Two additional points

As usual at cloudscale, snapshots are charged to the second. The storage space costs only half the regular price of NVMe SSD or bulk volumes (depending on the volume to which the snapshot refers). You will find the costs of your snapshots listed separately in the "Billing" area of the cloud control panel.

Snapshots make it possible to restore one or more volumes of a server to an earlier state. However, please be aware that they do not replace a proper backup. On the one hand, snapshots are saved in the same storage cluster as the original volumes here at cloudscale and a potential failure might affect both. For maximum security and independence we recommend that you always keep a copy of your important data outside our infrastructure. On the other hand, snapshots are designed to restore a volume as a whole. It is not possible only to restore selective data from the snapshot.

Volume snapshots are the perfect solution to ensure that you can return to an earlier state within the shortest amount of time after changes – whether for tests, training or as a safety net when upgrading critical servers. Quick to create and inexpensive, a snapshot may be able to save you a great deal of hassle. The "undo button" where it really matters!

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