> ## 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.

# Live vCPU & RAM Scaling

> Scale instance vCPU and memory in real-time without rebooting. Configure hot-add flavors and manage resource envelopes.

## Overview

Live vCPU and RAM scaling adjusts an instance's compute resources while it is running —
no reboot required. This is distinct from the standard resize operation, which requires
a reboot. Live scaling uses a combination of CPU hotplug, memory balloon, DIMM hotplug,
and virtio-mem to adjust resources within the bounds defined by the instance's flavor.

<Info>
  **Xloud-Developed** — Bidirectional CPU hotplug (add AND remove vCPUs) and
  combined memory scaling (balloon + DIMM + virtio-mem) are developed by Xloud and
  ship with XAVS / XPCI.
</Info>

<Note>
  **Prerequisites**

  * An instance in `Active` status with a hot-add-enabled flavor
  * The flavor must have `hw:cpu_min` or `hw:mem_min` extra specs set
  * The instance must not be locked
</Note>

***

## Adjust Resources (Dashboard)

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    <Steps titleSize="h3">
      <Step title="Open the Resource Adjustment dialog">
        Navigate to **Compute > Instances**. Click the **More** dropdown on the
        instance row, then select **Adjust Resources** under the **Configuration
        Update** group.

        <Note>
          This action is only available for instances in `Active` status whose
          flavor has hot-add enabled (`hw:cpu_min` or `hw:mem_min` extra specs).
          If the flavor does not support hot-add, this action does not appear.
        </Note>
      </Step>

      <Step title="Adjust vCPU and memory">
        The dialog shows:

        | Field              | Description                                                                 |
        | ------------------ | --------------------------------------------------------------------------- |
        | **Instance**       | Instance name (read-only)                                                   |
        | **Current Info**   | Current vCPU count and memory allocation (read-only)                        |
        | **vCPUs**          | Slider input — adjust between minimum and maximum vCPUs                     |
        | **Memory (GiB)**   | Slider input — adjust between minimum and maximum memory (0.25 GiB steps)   |
        | **Make permanent** | Checkbox — persist the configuration after a soft reboot (default: checked) |

        The vCPU slider step aligns to the CPU thread count configured in the flavor.
        The memory slider uses 0.25 GiB increments.

        The dialog fetches the live instance status to determine current and
        allowed resource ranges. Color-coded hints indicate the scaling method:

        | Color  | Meaning                                          |
        | ------ | ------------------------------------------------ |
        | Green  | virtio-mem — fully adjustable in both directions |
        | Yellow | No balloon driver detected — limited scaling     |
        | Blue   | DIMM hotplug information                         |
      </Step>

      <Step title="Apply the adjustment">
        Click **Confirm**. The resources are adjusted immediately while the
        instance continues running.

        <Check>
          Instance vCPU and memory updated in real-time. Verify from the instance
          detail page or by running `nproc` / `free -h` inside the guest.
        </Check>
      </Step>
    </Steps>
  </Tab>

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

    ```bash title="Check current live resource status" theme={null}
    openstack server show <INSTANCE_ID> -c "xloud-status"
    ```

    ```bash title="Adjust vCPU count" theme={null}
    curl -X POST -H "X-Auth-Token: $TOKEN" \
      -H "Content-Type: application/json" \
      -d '{"current_vcpus": 4}' \
      "$NOVA_ENDPOINT/v2.1/os-xloud-adjust/<INSTANCE_ID>"
    ```

    ```bash title="Adjust memory" theme={null}
    curl -X POST -H "X-Auth-Token: $TOKEN" \
      -H "Content-Type: application/json" \
      -d '{"current_memory_mb": 8192}' \
      "$NOVA_ENDPOINT/v2.1/os-xloud-adjust/<INSTANCE_ID>"
    ```

    <Note>
      Live resource adjustment uses the Xloud-developed Nova API extension.
      The `openstack` CLI does not have a native command for this operation.
    </Note>
  </Tab>
</Tabs>

***

## Configure Hot-Add Flavors

To enable live scaling, create flavors with hot-add parameters:

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    When creating a flavor (see [Flavor Management](/services/compute/flavors)),
    enable the **Hot-Add** toggle in the **Step 1 (Params Setting)** section.
    Configure:

    | Field                    | Description                                                      |
    | ------------------------ | ---------------------------------------------------------------- |
    | **Enable Hot-Add**       | Set to Yes                                                       |
    | **Minimum CPU**          | Starting vCPU count at boot (can scale up to flavor's max vCPUs) |
    | **Minimum Memory (GiB)** | Starting memory at boot (can scale up to flavor's max memory)    |

    The instance boots with the minimum resources and can be scaled up to the
    flavor's maximum without rebooting.
  </Tab>

  <Tab title="CLI" icon="terminal">
    ```bash title="Create a hot-add enabled flavor" theme={null}
    openstack flavor create \
      --vcpus 8 --ram 16384 --disk 0 \
      --public \
      hotadd.large

    openstack flavor set \
      --property hw:cpu_min=2 \
      --property hw:mem_min=4096 \
      hotadd.large
    ```

    This creates a flavor where instances boot with 2 vCPUs / 4 GiB RAM and
    can scale up to 8 vCPUs / 16 GiB RAM while running.
  </Tab>
</Tabs>

***

## Next Steps

<CardGroup cols={2}>
  <Card title="Resize an Instance" href="/services/compute/resize-instance" color="#197560">
    Change flavors entirely (requires reboot) for capacity beyond hot-add range
  </Card>

  <Card title="Flavors" href="/services/compute/flavors" color="#197560">
    Create and manage flavors with hot-add configuration
  </Card>

  <Card title="Launch an Instance" href="/services/compute/launch-instance" color="#197560">
    Launch instances with hot-add enabled flavors
  </Card>

  <Card title="Troubleshooting" href="/services/compute/troubleshooting" color="#197560">
    Resolve live scaling failures and balloon driver issues
  </Card>
</CardGroup>