> ## 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.

# Image Formats

> Compare QCOW2, RAW, VHD, and VMDK image formats and choose the right one for your Xloud workloads.

## Overview

The Xloud Image Service supports multiple virtual disk formats. Selecting the right format
affects launch performance, storage efficiency, and compatibility with your source
environment. This guide compares supported formats, explains conversion workflows, and
provides recommendations for common use cases.

<Note>
  **Prerequisites**

  * Basic familiarity with virtual disk concepts
  * `qemu-img` installed locally for format conversion (optional)
</Note>

***

## Format Comparison

| Format         | Extension       | Copy-on-Write     | Compression | Best For                                                   |
| -------------- | --------------- | ----------------- | ----------- | ---------------------------------------------------------- |
| **QCOW2**      | `.qcow2`        | Yes               | Yes         | Default. General-purpose workloads, fast snapshot support. |
| **RAW**        | `.img`, `.raw`  | No (storage-side) | No          | Maximum performance on Ceph-backed storage.                |
| **VHD / VHDX** | `.vhd`, `.vhdx` | Fixed/Dynamic     | —           | Images migrated from Hyper-V.                              |
| **VMDK**       | `.vmdk`         | Sparse/Flat       | —           | Images migrated from VMware.                               |

***

## Format Details

<AccordionGroup>
  <Accordion title="QCOW2 — Recommended" icon="layers" defaultOpen>
    QCOW2 (QEMU Copy-On-Write v2) is the default and recommended format for Xloud.
    It supports thin provisioning (only stores data that has been written), internal
    snapshots, compression, and optional AES encryption.

    | Property      | Value                                                            |
    | ------------- | ---------------------------------------------------------------- |
    | Extension     | `.qcow2`                                                         |
    | Copy-on-write | Yes                                                              |
    | Compression   | Yes                                                              |
    | Maximum size  | No limit                                                         |
    | Best for      | General-purpose workloads, fast launch times, snapshot workflows |

    Create a new empty QCOW2 image:

    ```bash title="Create empty 20GB QCOW2 image" theme={null}
    qemu-img create -f qcow2 my-disk.qcow2 20G
    ```
  </Accordion>

  <Accordion title="RAW — Maximum Performance" icon="zap">
    RAW images are unformatted disk dumps. There is zero overhead from the format layer.
    When Xloud Distributed Storage (Ceph RBD) is the image and volume backend, RBD handles
    copy-on-write natively — making RAW the optimal format.

    | Property      | Value                                                  |
    | ------------- | ------------------------------------------------------ |
    | Extension     | `.img` or `.raw`                                       |
    | Copy-on-write | No (handled by storage backend)                        |
    | Compression   | No                                                     |
    | Best for      | Performance-sensitive workloads on Ceph-backed storage |

    <Tip>
      On Ceph-backed deployments, instance launches from RAW images use zero-copy RBD clones
      — resulting in near-instantaneous boot times regardless of image size.
    </Tip>
  </Accordion>

  <Accordion title="VHD / VHDX — Hyper-V Migration" icon="arrow-right-left">
    VHD and VHDX are the native disk formats for Microsoft Hyper-V. Import them directly
    into Xloud when migrating workloads from a Hyper-V environment.

    | Format | Source Platform | Notes                              |
    | ------ | --------------- | ---------------------------------- |
    | VHD    | Hyper-V (Gen 1) | Fixed and dynamic VHDs supported   |
    | VHDX   | Hyper-V (Gen 2) | Preferred format for Hyper-V 2012+ |

    <Tip>
      Convert VHD/VHDX to QCOW2 after import for optimal performance and Xloud snapshot support.
    </Tip>
  </Accordion>

  <Accordion title="VMDK — VMware Migration" icon="server">
    VMDK is the native disk format for VMware ESXi and Workstation. Import VMDKs directly
    when migrating virtual machines from a VMware environment.

    | Format      | Notes                                           |
    | ----------- | ----------------------------------------------- |
    | Sparse VMDK | Thin-provisioned. Import directly.              |
    | Flat VMDK   | Pre-allocated. Larger file, no format overhead. |

    <Tip>
      Convert VMDKs to QCOW2 after import to enable Xloud snapshot and resize operations.
    </Tip>
  </Accordion>
</AccordionGroup>

***

## Convert Between Formats

Use `qemu-img` to convert images locally before upload:

<CodeGroup>
  ```bash title="VHD to QCOW2" theme={null}
  qemu-img convert -f vpc -O qcow2 windows-server.vhd windows-server.qcow2
  ```

  ```bash title="VMDK to QCOW2" theme={null}
  qemu-img convert -f vmdk -O qcow2 vm-disk.vmdk vm-disk.qcow2
  ```

  ```bash title="RAW to QCOW2" theme={null}
  qemu-img convert -f raw -O qcow2 disk.img disk.qcow2
  ```

  ```bash title="QCOW2 to RAW" theme={null}
  qemu-img convert -f qcow2 -O raw ubuntu.qcow2 ubuntu.img
  ```
</CodeGroup>

Verify the converted image:

```bash title="Verify converted image" theme={null}
qemu-img info disk.qcow2
```

***

## Next Steps

<CardGroup cols={2}>
  <Card title="Upload an Image" href="/services/images/upload-image" color="#197560">
    Upload your converted image to the Xloud Image Service.
  </Card>

  <Card title="Image Properties" href="/services/images/image-properties" color="#197560">
    Set hardware properties matching your image format and source platform.
  </Card>

  <Card title="Image Admin Guide — Storage Backends" href="/services/images/storage-backends" color="#197560">
    Configure the storage backend where images are stored after upload.
  </Card>

  <Card title="Troubleshooting" href="/services/images/troubleshooting" color="#197560">
    Resolve format-related launch failures and image upload errors.
  </Card>
</CardGroup>