Windows Performance Optimization in OpenStack

Running Windows instances in OpenStack often requires additional tuning to achieve optimal performance. By default, OpenStack uses generic hardware models that may not provide the best results for Windows workloads.

This guide outlines key image properties and configuration choices that can significantly improve Windows instance performance.

Recommended Image Properties

When uploading or updating a Windows image, set the following properties:

openstack image create \
    --property os_type=windows \
    --property hw_machine_type=q35 \
    --property hw_disk_bus=scsi \
    --property hw_scsi_model=virtio-scsi
    <windows_image_name>

• os_type=windows enables Windows-specific handling in the compute driver For details on available enlightenments that can be exposed to the guest, see Hyper-V Enlightenments

• hw_machine_type=q35 provides a modern PCIe-based machine type, improving compatibility and performance for newer Windows versions

• hw_disk_bus=scsi attaches disks using a SCSI controller instead of IDE or default models

• hw_scsi_model=virtio-scsi enables a paravirtualized SCSI controller, improving performance and scalability compared to legacy disk models

Note

• Ensure that VirtIO drivers are installed inside the Windows guest (especially for SCSI and network devices)

• These properties must be applied before instance creation, changes require rebuilding or recreating the instance

Using optimized image properties such as q35, virtio-scsi, and scsi disk bus can significantly improve Windows instance performance in OpenStack environments, especially for I/O intensive workloads.

In the 2026.1 release cycle, support for enabling I/O threads (iothreads) in Nova has been introduced. This can further improve disk I/O performance, especially for Windows workloads.