open-nomad/website/content/docs/job-specification/ephemeral_disk.mdx

---
layout: docs
page_title: ephemeral_disk Block - Job Specification
description: |-
  The "ephemeral_disk" block describes the ephemeral disk requirements of the
  group. Ephemeral disks can be marked as sticky and support live data
  migrations.
---

# `ephemeral_disk` Block

<Placement groups={['job', 'group', 'ephemeral_disk']} />

The `ephemeral_disk` block describes the ephemeral disk requirements of the
group. Ephemeral disks can be marked as sticky and support live data migrations.
All tasks in this group will share the same ephemeral disk.

```hcl
job "docs" {
  group "example" {
    ephemeral_disk {
      migrate = true
      size    = 500
      sticky  = true
    }
  }
}
```
The ephemeral disk can be referenced under `alloc/data/`. More information can be found in the [filesystem internals].

## `ephemeral_disk` Parameters

- `migrate` `(bool: false)` - When `sticky` is true, this specifies that the
  Nomad client should make a best-effort attempt to migrate the data from a
  remote machine if placement cannot be made on the original node. During data
  migration, the task will block starting until the data migration has
  completed. Migration is atomic and any partially migrated data will be
  removed if an error is encountered.

- `size` `(int: 300)` - Specifies the size of the ephemeral disk in MB. The
  current Nomad ephemeral storage implementation does not enforce this limit;
  however, it is used during job placement.

- `sticky` `(bool: false)` - Specifies that Nomad should make a best-effort
  attempt to place the updated allocation on the same machine. This will move
  the `local/` and `alloc/data` directories to the new allocation.

## `ephemeral_disk` Examples

The following examples only show the `ephemeral_disk` blocks. Remember that the
`ephemeral_disk` block is only valid in the placements listed above.

### Sticky Volumes

This example shows enabling sticky volumes with Nomad using ephemeral disks:

```hcl
ephemeral_disk {
  sticky = true
}
```

[resources]: /nomad/docs/job-specification/resources 'Nomad resources Job Specification'
[filesystem internals]: /nomad/docs/concepts/filesystem#templates-artifacts-and-dispatch-payloads 'Filesystem internals documentation'