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Citrix Hypervisor 8.1

Citrix have released a new version of Citrix Hypervisor 8.1 (aka XenServer)

I am very excited about this release because now Citrix is supporting the new AMD latest Rome CPU and support multiple NVIDIA vGPU and guest UEFI secure boot. The Citrix Hypervisor platform has been updated to use Xen hypervisor version 4.13. Lots of new features ūüôā

What is new in Citrix Hypervisor 8.1

Citrix Hypervisor 8.1 provides the following new features and enhancements

  • Guest UEFI boot and Secure Boot
  • Multiple vGPU
  • Citrix Hypervisor ‚Äď Performance improvements
  • Changes to guest operating system support
  • Changes to processor support
  • Citrix Hypervisor Conversion Manager console capabilities are now included in XenCenter
  • Update to Xen hypervisor
  • PVS accelerator optimised for Citrix Hypervisor 8.1

Citrix Hypervisor 8.1 is a Current Release (CR). The Current Release model allows customers to consume new features at the earliest possible juncture. A Current Release contrasts with the Long Term Service Release (XenServer 7.1 LTSR), which guarantees stability in terms of the feature set.

Citrix Hypervisor 8.1 is available in the following editions:

  • Premium Edition (previously Enterprise Edition)
  • Standard Edition
  • Express Edition (previously Free Edition)

New features and improvements in Citrix Hypervisor 8.1

Citrix Hypervisor 8.1 introduces enhanced features and functionality for application, desktop, and server virtualization use cases. All Citrix Hypervisor 8.1 features are available to all licensed Citrix Virtual Apps and Desktops (formerly XenApp and XenDesktop) customers.

Guest UEFI boot and Secure Boot

Citrix Hypervisor enables VMs running Windows 10 (64-bit), Windows Server 2016 (64-bit), or Windows Server 2019 (64-bit) to boot in UEFI mode. UEFI boot provides a richer interface for the guest operating systems to interact with the hardware, which can significantly reduce Windows VM boot times.

For these Windows operating systems, Citrix Hypervisor also supports Windows Secure Boot. Secure Boot prevents unsigned, incorrectly signed or modified binaries from being executed during boot. Secure Boot also reduces the risk that malware in the guest can manipulate the boot files or run during the boot process.

Multiple vGPU

Multiple vGPU enables multiple virtual GPUs to be used concurrently by a single VM. Only certain vGPU profiles can be used and all vGPUs attached to a single VM must be of the same type. These additional vGPUs can be used to perform computational processing. For more information about the number of vGPUs supported for a single VM, see Configuration Limits.

This feature is only available for NVIDIA GPUs. For more information about the physical GPUs that support multiple vGPU, see the NVIDIA documentation.

For NVIDIA GPUs and drivers that support multiple vGPU, you can configure a single VM to use multiple virtual GPUs concurrently. These additional vGPUs can be used to perform computational processing. Only certain vGPU profiles can be used and all vGPUs attached to a single VM must be of the same type.

Multiple vGPU Vendor support

The following table lists GPU, shared GPU, and multiple vGPU support for guests:


Only a subset of guest operating systmes support multiple vGPU. For more information, see Guest support and constraints.

You might need a vendor subscription or a license depending on the graphics card used.

Supported NVIDIA Multiple vGPUs to a single VM

Only Q-series¬†and C-series¬†vGPUs that are allocated all of the physical GPU’s frame buffer are supported.

Maximum vGPUs per VM

NVIDIA vGPU software supports up to a maximum of four vGPUs per VM on Citrix XenServer 8.1.

Supported Hypervisor Releases

Citrix XenServer 8.1 and later compatible updates only.

2.7. Peer-to-Peer CUDA Transfers over NVLink Support

Peer-to-peer CUDA transfers enable device memory between vGPUs on different GPUs that are assigned to the same VM to be accessed from within the CUDA kernels. NVLink is a high-bandwidth interconnect that enables fast communication between such vGPUs. Peer-to-Peer CUDA Transfers over NVLink is supported only on a subset of vGPUs, Citrix Hypervisor 8.1 releases, and guest OS releases.

Supported vGPUs

Only Q-series and C-series vGPUs that are allocated all of the physical GPU’s frame buffer on physical GPUs that support NVLink are supported.

Supported Hypervisor Releases

Peer-to-Peer CUDA Transfers over NVLink are supported on all hypervisor releases that support the assignment of more than one vGPU to a VM.

Supported Guest OS Releases

Linux only. Peer-to-Peer CUDA Transfers over NVLink are not supported on Windows.


  • Only direct connections are supported. NVSwitch is not supported.
  • PCIe is not supported.
  • SLI is not supported.

Citrix Hypervisor – Performance improvements

Improved performance for VM imports and exports that use the XVA format

Changes to the checksum used in XVA files in Citrix Hypervisor 8.1 provide significant performance improvements when importing or exporting VMs using this new checksum algorithm.

The reduction in the time it takes to import or export a VM depends on the specific hardware of the machine. The larger the VM the larger the performance improvement seen.

Use XenCenter 8.1 to manage exported VMs that use XVA files with the new checksum algorithm.

If you have a custom application that relies on the format of the checksum included in the XVA file, update your application to use the new format. The checksum has changed to use the xxHash algorithm. The checksum file name now ends with the extension .xxhash.

Storage performance improvements

Citrix Hypervisor 8.1 includes the following performance enhancements to storage:

  • Storage performance is significantly improved when I/O is performed in block sizes larger than 64 KiB on an NFS SR.
  • Multipage support is now available in non-GFS2 SRs for better storage performance. If your Windows VM has the Citrix VM Tools installed, the VM uses multipage support automatically. To enable multipage support on a Linux VM complete the following steps:
    1. On the VM, run the following command: echo 'options xen_blkfront max_ring_page_order=3' >/etc/modprobe.d/xen_blkfront.conf
    2. Depending on your Linux distribution, run one of the following commands:
      • For RHEL, CentOS, or Oracle Enterprise Linux:¬†dracut -f -v
      • For Debian-based distributions:¬†update-initramfs -u -k all
    3. Reboot your VM.

New Windows I/O drivers with improved performance

Updated Windows I/O drivers with the major version 9 (9.x.x.x) are provided with this release of Citrix Hypervisor for the following operating systems: Windows 8.1, Windows 10, Windows Server 2012, Windows Server 2012 R2, Windows Server 2016, Windows Server Core 2016, Windows Server 2019, Windows Server Core 2019. These Windows I/O drivers include a number of performance improvements.

These drivers are also available through Windows Update for Premium Edition customers.

Windows I/O drivers with the major version 8 (8.x.x.x) are still provided for the older supported Windows operating systems. These drivers do not contain the performance improvements.

Changes to guest operating system support

The set of guest operating systems that Citrix Hypervisor supports has been updated. For more information, see Guest operating system support


Citrix Hypervisor now supports the following additional guest operating systems:

  • SUSE Linux Enterprise Server 12 SP4 (64-bit)
  • SUSE Linux Enterprise Desktop 12 SP4 (64-bit)
  • SUSE Linux Enterprise Server 15 SP1 (64-bit)
  • SUSE Linux Enterprise Desktop 15 SP1 (64-bit)
  • Red Hat Enterprise Linux 8 (64-bit)
  • Oracle Enterprise Linux 8 (64-bit)
  • CentOS 8 (64-bit)
  • Debian Buster 10 (64-bit)


The following guest operating system requirements changed in Citrix Hypervisor 8.1:

  • Windows 10In previous releases of Citrix Hypervisor, the minimum disk space supported for Windows 10 was 24 GB. It is now 32 GB for new Windows 10 VMs. For more information, see¬†What‚Äôs new in Windows 10, version 1903.

Changes to processor support

The following processors are now supported in Citrix Hypervisor 8.1:

  • AMD EPYC 7xx2(P)

For more information, see the Hardware Compatibility List.

Citrix Hypervisor Conversion Manager console capabilities are now included in XenCenter

In Citrix Hypervisor 8.0 and earlier, a separate Conversion Manager console was provided. From Citrix Hypervisor 8.1, this capability is integrated into XenCenter. The legacy Citrix Hypervisor Conversion Manager console has been retired.

The conversion plugin that was previously included in the Citrix Hypervisor server installation has also been removed from Citrix Hypervisor 8.1. The removal of this plugin means that you must use the latest version of XenCenter, which includes the conversion capability, with Citrix Hypervisor 8.1. (You cannot use older versions of the Conversion Manager console with Citrix Hypervisor 8.1.)

However, the Conversion Manager virtual appliance is still required for converting VMware VMs to Citrix Hypervisor VMs. This component is provided on the Citrix Hypervisor Product Download page.

For more information, see Convert VMware workloads.

XenCenter alerts for end of life or end of support

XenCenter now alerts you when the version of your managed Citrix Hypervisor servers is approaching end of life or reaches end of life. For more information, see XenCenter Alerts.

XenCenter also alerts you when a Current Release or Cumulative Update is approaching or has passed a date when there will be no further hotfixes issued for that release. Act upon this information and update your environment to a later supported release, to ensure that updates to address any future functional and security related issues can be applied.

Update to Xen hypervisor

The Citrix Hypervisor platform has been updated to use Xen hypervisor version 4.13.

In addition, version changes to the Xen hypervisor can now be applied as an update, either through a hotfix or in a subsequent release.



Citrix Hypervisor 8.1 documentation/release notes
Citrix Hypervisor 8.1 GPU overview

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