Volumes

Volumes are properties of services that specify where and how a service stores its data.

You can use volumes to configure services to store their data in external storage systems, outside of the system instances. This allows data to be more easily backed up or migrated.

Volumes can also allow services to store different types of data in different locations. For example, a service might use two separate volumes, one for storing its logs and the other for storing all other data.

Example

In this example, service A runs on instance 101. The service's Log volume stores data in a folder on the system instance and the service's Data volume stores data in an NFS mount.

Creating and managing volumes

Depending on how they are created and managed, volumes are separated into these groups:

• System-managed volumes are created and managed by the system. When you deploy the system, you can specify the volume driver and options that the system should use when creating these volumes.

  After the system is deployed, you cannot change the configuration settings for these volumes.

• User-managed volumes can be added to services and job types after the system has been deployed. These are volumes that you manage; you need to create them on your system instances before you can configure a service or job to use them.
  Note: As of release 1.3.0, none of the built-in services support adding user-managed volumes.

Volume drivers

When configuring a volume, you specify the volume driver that it should use. The volume driver determines how and where data is stored.

Because services run in Docker containers on instances in the system, volume drivers are provided by Docker and other third-party developers, not by the system itself. For information about volume drivers you can use, see the applicable Docker or third-party developer's documentation.

By default, all services do not use volume drivers but instead use the bind-mount setting. With this setting, data for each service is stored within the system installation folder on each instance where the service runs.

For more information on volume drivers, see the Docker documentation.