Discover how to create stateful workloads

Nomad allows users to mount persistent data from local or remote storage volumes into task environments in several ways:

• Container Storage Interface (CSI) plugins
• Nomad dynamic host volumes
• Nomad static host volumes
• Task driver specific volumes, such as Docker volume drivers

Nomad's Container Storage Interface (CSI) integration can manage external storage volumes for stateful workloads running inside your cluster. CSI providers are third-party plugins that run as Nomad jobs and can orchestrate the creation and mounting of volumes created by your cloud or storage provider. AWS Elastic Block Storage, Azure disk, GCE Persistent Disk, and Alicloud Disk are a few of the available block-device plugins available as CSI plugins. You can find a more comprehensive list in the CSI Developer Documentation

Nomad is aware of CSI-managed volumes during the scheduling process, enabling it to schedule your workloads based on the availability of volumes on a specific client.

Nomad's host volumes come in two types - dynamic and static. Dynamic host volumes are, similar to CSI volumes, managed by Nomad with the help of plugins. The plugin creates the volumes and mounts them on the client, and Nomad makes the volumes available to the task group. Plugins follow a specification that allows anyone to write a plugin for their storage needs.

Static Host volumes allow you to mount any existing directory on the Nomad client into an allocation. These directories can be directories on a client, but can also be mounted networked or clustered filesystems like NFS, SeaweedFS or GlusterFS. Static host volumes are defined in the client configuration file and are available to all tasks running on that client.

The Docker task driver's support for volumes enables Nomad to integrate with software-defined storage (SDS) solutions that have native support for Docker. Keep in mind that Nomad does not actually manage storage pools or replication as these tasks are delegated to the SDS providers. Please assess all factors and risks when utilizing such providers to run stateful workloads (such as your production database).

For more information on the various options for stateful storage in Nomad, refer to the Considerations for Stateful Workloads Workloads guide.

In these guides, you will deploy a stateful application to a Nomad cluster and demonstrate that the data is persisted beyond the life of the allocation.