> ## 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.

# Server Groups

> Control instance placement across physical hosts using affinity and anti-affinity policies. Create and manage server groups in the Xloud Dashboard or CLI.

## Overview

Server groups enforce placement policies that determine how a set of instances is
distributed across physical compute hosts. Use server groups to guarantee high availability
through host separation, improve performance through co-location, or meet compliance
requirements for workload isolation.

<Note>
  **Prerequisites**

  * An active Xloud project
  * At least two compute hosts available (required for `anti-affinity` enforcement)
  * Sufficient server group quota
</Note>

***

## Placement Policies

| Policy                 | Behavior                                                         | Failure Mode                                                    |
| ---------------------- | ---------------------------------------------------------------- | --------------------------------------------------------------- |
| **affinity**           | All instances placed on the **same** physical host               | Launch fails if the target host cannot accommodate the instance |
| **anti-affinity**      | Each instance placed on a **different** physical host            | Launch fails if insufficient distinct hosts are available       |
| **soft-affinity**      | Prefer the same host; allow different hosts if required          | Launch succeeds even when co-location is not possible           |
| **soft-anti-affinity** | Prefer different hosts; allow same host if no alternative exists | Launch succeeds even when distinct hosts are unavailable        |

<Tip>
  Use `anti-affinity` for production replicated services (web tiers, application clusters,
  database replicas) where a single host failure must not take down all instances simultaneously.
  Use `soft-anti-affinity` when you want best-effort separation without hard placement failures.
</Tip>

***

## Create a Server Group

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    <Steps titleSize="h3">
      <Step title="Navigate to Server Groups">
        Navigate to **Compute > Server Groups** in the sidebar.
        Click **Create Server Group**.
      </Step>

      <Step title="Configure the server group">
        | Field      | Type       | Required | Description                            |
        | ---------- | ---------- | -------- | -------------------------------------- |
        | **Name**   | Text input | Yes      | Human-readable name for the group      |
        | **Policy** | Dropdown   | Yes      | Placement policy — see the table above |

        The dropdown options are:

        * `affinity` — instances on same physical machine (mandatory)
        * `anti-affinity` — instances on different machines (mandatory)
        * `soft-affinity` — same machine preferred (best effort)
        * `soft-anti-affinity` — different machines preferred (best effort)

        The dialog also displays your current **Server Groups** quota usage
        (used / limit). If your quota is exhausted, the submit button is disabled.
      </Step>

      <Step title="Create the group">
        Click **Confirm**. The server group appears in the list.

        <Check>Server group appears in the list with the selected policy.</Check>
      </Step>
    </Steps>
  </Tab>

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

    <CodeGroup>
      ```bash title="Create anti-affinity group" theme={null}
      openstack server group create \
        --policy anti-affinity \
        ha-web-tier
      ```

      ```bash title="Create soft-affinity group" theme={null}
      openstack server group create \
        --policy soft-affinity \
        collocated-cache
      ```
    </CodeGroup>
  </Tab>
</Tabs>

***

## View Server Groups

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    Navigate to **Compute > Server Groups**. The list shows:

    | Column           | Description                                  |
    | ---------------- | -------------------------------------------- |
    | **ID/Name**      | Group identifier (clickable to view details) |
    | **Member Count** | Number of instances in the group             |
    | **Policy**       | Placement policy                             |

    Filter by **Name** or **Policy** using the search/filter bar.

    Click a group name to view the detail page, which shows the **Members** tab
    listing all instances assigned to this server group.
  </Tab>

  <Tab title="CLI" icon="terminal">
    <CodeGroup>
      ```bash title="List server groups" theme={null}
      openstack server group list
      ```

      ```bash title="Show server group details" theme={null}
      openstack server group show <GROUP_ID>
      ```
    </CodeGroup>
  </Tab>
</Tabs>

***

## Launch Instances in a Server Group

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    When creating an instance, expand the **Advanced Options** section in **Step 3
    (System Config)** of the wizard. Select your server group from the **Server Group**
    table.

    Alternatively, from the server group detail page, click the **Create Instance**
    action in the **More** dropdown. The server group is pre-selected in the wizard.
  </Tab>

  <Tab title="CLI" icon="terminal">
    ```bash title="Launch instance in a server group" theme={null}
    openstack server create \
      --image <IMAGE_ID> \
      --flavor <FLAVOR> \
      --network <NETWORK> \
      --hint group=<SERVER_GROUP_ID> \
      my-instance
    ```
  </Tab>
</Tabs>

***

## Delete a Server Group

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    Navigate to **Compute > Server Groups**. Click the **Delete** action (the first
    row action) on the group row. Confirm the deletion in the dialog.

    <Danger>
      Deleting a server group removes the placement constraint. Existing instances
      are not affected, but new launches will no longer enforce the policy.
    </Danger>
  </Tab>

  <Tab title="CLI" icon="terminal">
    ```bash title="Delete a server group" theme={null}
    openstack server group delete <GROUP_ID>
    ```
  </Tab>
</Tabs>

***

## Next Steps

<CardGroup cols={2}>
  <Card title="Launch an Instance" href="/services/compute/launch-instance" color="#197560">
    Create instances with server group placement in the 4-step wizard
  </Card>

  <Card title="Availability Zones" href="/services/compute/availability-zones" color="#197560">
    Understand fault domains and zone-level placement
  </Card>

  <Card title="Live Migration" href="/services/compute/live-migration" color="#197560">
    Move instances between hosts while respecting group policies
  </Card>

  <Card title="Troubleshooting" href="/services/compute/troubleshooting" color="#197560">
    Resolve placement failures and group member limit issues
  </Card>
</CardGroup>