> ## Documentation Index
> Fetch the complete documentation index at: https://docs.xloud.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Availability Zones

> Partition your compute cluster into independent fault domains. Select availability zones during instance launch.

## Overview

Availability zones partition the compute cluster into independent fault domains. Each
zone typically represents a separate rack, power circuit, or physical location. Placing
instances across multiple zones protects against localized hardware failures.

<Note>
  **Prerequisites**

  * At least one availability zone configured by your administrator
  * Zones are configured through [Host Aggregates](/services/compute/scheduling)
</Note>

***

## Select an Availability Zone at Launch

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    During instance creation, the **Available Zone** field appears in **Step 1
    (Base Config)** of the wizard.

    | User Type          | Options Shown                                                                                                               |
    | ------------------ | --------------------------------------------------------------------------------------------------------------------------- |
    | **Regular users**  | Dropdown of available zone names                                                                                            |
    | **Administrators** | Grouped options — **Available Zones** (zone names) plus **Pin to Host** (`zone:hostname` entries for direct host placement) |

    <Tip>
      If you do not select a specific zone, the scheduler automatically chooses
      the zone with the most available resources. This is recommended for most
      workloads.
    </Tip>

    For high availability, launch replicated instances in different zones using a
    [Server Group](/services/compute/server-groups) with `anti-affinity` policy.
  </Tab>

  <Tab title="CLI" icon="terminal">
    ```bash title="Source credentials" theme={null}
    source openrc.sh
    ```

    <CodeGroup>
      ```bash title="List availability zones" theme={null}
      openstack availability zone list --compute
      ```

      ```bash title="Launch in a specific zone" theme={null}
      openstack server create \
        --image <IMAGE_ID> \
        --flavor <FLAVOR> \
        --network <NETWORK> \
        --availability-zone <ZONE_NAME> \
        my-instance
      ```

      ```bash title="Launch on a specific host (admin)" theme={null}
      openstack server create \
        --image <IMAGE_ID> \
        --flavor <FLAVOR> \
        --network <NETWORK> \
        --availability-zone <ZONE_NAME>:<HOSTNAME> \
        my-instance
      ```
    </CodeGroup>
  </Tab>
</Tabs>

***

## Zone Management

Availability zones are managed through Host Aggregates by administrators. See
[Compute Scheduling](/services/compute/scheduling) for creating aggregates with
zone assignments.

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    Navigate to **Compute > Host Aggregates** in the admin sidebar. The
    **Availability Zones** tab shows a read-only list of all configured zones.

    To create a new zone, create a Host Aggregate and assign it a new availability
    zone name during creation.
  </Tab>

  <Tab title="CLI" icon="terminal">
    <CodeGroup>
      ```bash title="List zones" theme={null}
      openstack availability zone list --compute
      ```

      ```bash title="Create zone via aggregate" theme={null}
      openstack aggregate create --zone new-zone my-aggregate
      openstack aggregate add host my-aggregate <HOSTNAME>
      ```
    </CodeGroup>
  </Tab>
</Tabs>

***

## Next Steps

<CardGroup cols={2}>
  <Card title="Launch an Instance" href="/services/compute/launch-instance" color="#197560">
    Select an availability zone in the instance create wizard
  </Card>

  <Card title="Server Groups" href="/services/compute/server-groups" color="#197560">
    Combine zones with anti-affinity for maximum resilience
  </Card>

  <Card title="Scheduling" href="/services/compute/scheduling" color="#197560">
    Create host aggregates and manage zone assignments
  </Card>

  <Card title="Compute Hosts" href="/services/compute/compute-hosts" color="#197560">
    View which hosts belong to which zones
  </Card>
</CardGroup>