Category: Hypervisor



PVS-Accelerator is a feature for Citrix Hypervisor (previously named XenServer). The feature utilizes the local storage and RAM on Dom0 on each Citrix Hypervisor and caches read requests from a provisioned target device. It saves network, CPU and Provisioning host disk I/O resources, effectively improving performance. Overall your storage and network should see an improvement if they are under heavy load today. [1]

Network Bandwidth Utilization
Network Bandwidth Utilization [2]

PVS-Accelerator helps with improved end-user experience, accelerated VM boots and boot storm, simplified scale-out by adding more hypervisor hosts and fewer provisioning servers are needed.


  • XenServer PVS-Accelerator feature is only available in Citrix Hypervisor 7.1 and Provisioning 7.13 or later
  • PVS-Accelerator is available for customer with XenServer Enterprise Edition or if you have XenDesktop/XenApp licenses
  • If you have a Citrix Hypervisor 7.1 <, Provisioning 7.13 < and XenApp/XenDesktop you should be able to utilize the feature without any extra license or upgrades in considerations [3]


There is no need to reboot XS host to enable PVS-accelerator. Unless you have less than 4 GB on Dom0, which is required to enable the feature. Also notice that the recommended Cache Size on storage repository is 5 GB for every vDisk version actively provisioned.

PVS-Acceleration configuration
PVS-Acceleration configuration
  • PVS-Accelerator only caches reads from vDisk, but not writes or reads from a write cache. Support is for vDisks with any non-persistent write cache type, but not “Cache on Server, Persistent” or “Cache on device hard disk persisted” write cache type
  • If you have more than one virtual network interface (VIF), make sure that the first VIF of a VM is used for connecting to the Provisioning Server
  • If you have multiple Provisioning servers that are deployed with HA and the same VHD, but have different file system timestamps, data may be cached multiple times. Due to this limitation, Citrix recommends using VHDX format, rather than VHD for vDisks
  • If you are running a 10 GBe network or just a few streamed VMs you will probably not notice a big difference


  • Lower network utilization
  • Faster VM Boot time (Around 60%)
  • Higher Provisioning server density
  • Improved logon time
  • Helps with a saturated network or branch office
Average VM Boot Time
Average VM Boot Time
Source: [4]

How to install

Installation is pretty straight-forward. You can download the PVS-Accelerator Supplemental Pack at (requires Citrix account).

  • Path: Downloads / Citrix Hypervisor (XenServer) / XenServer 7.1 LTSR or above (Any Edition) / Optional Components / PVS Accelerator Supplemental Pack
  • Download and install the .iso file from XenCenter
XenCenter - Install Update
XenCenter – Install Update
XenServer - Select updatre
XenServer – Select Update

A new tab will appear in XenCenter console. Select your Hypervisor pool and click the PVS tab. Configure the PVS-Accelerator by naming your site and cache configuration. [5]

Configure PVS Accelerator
Configure PVS-Accelerator

Next step is to go back to the Provisioning Console and create your VMs with PVS-Accelerator. You do this by right-clicking on your site and running the Setup Wizard. You cannot do this on your existing provisioned targets. The short explanation is that PVS-Accelerated VMs is tied to Provisioning servers with a UUID on the XenServer.

Note: If you were to re-install the XenServer where PVS-Accelerated VMs was enabled, Provisioning Services will become out of sync and you will need to delete previously configured VMs associated with the cache configuration, including host. And reconfigure PVS-Accelerator and setup the cache again. [6]

Provisioning Console - Streamed VM Setup Wizard
Provisioning Console – Streamed VM Setup Wizard

Be sure to select ”Enable PVS-Accelerator for all Virtual Machines” when configuring the number of VMs and their resources.

Provisioning Console - Enable PVS-Accelerator
Provisioning Console – Enable PVS-Accelerator
Provisioning Console - Streamed VM Wizard
Provisioning Console – Streamed VM Wizard

Verify that the PVS-Accelerator status is Caching your VMs from the XenCenter > Pool > PVS tab.

XenCenter - PVS Tab
XenCenter – PVS Tab








How to manually crash your VM on a XenServer

Sometimes you need to simulate or provoke a crash on a Virtual Machine to either verify a problem or get a Memory Dump to have a closer look at whats is happening with the Virtual Machine. The thing is, its quite tricky to do that manually. Lucky for you there is a quite simple way to achieve this on a XenServer and I will show every step of the way.

When your Virtual Machine (VM) is at the desired state you should do the following steps:

  1. Find out the VM ID the XenServer has provided the VM, this changes when rebooted so you need to make sure every time you do this, you cannot use the same ID again. First make note of the Virtual Machine UUID, you can find it under ”General” for the specific VM.

2. Now we need to find out the ID the XenServer provided for this specific VM. Go the the XenServer Console (the host of the VM) and type the following: list_domains 

As you can see it lists all the VM on this XenServer, and you will also see the ID provided correlated to the UUID. Make sure you have the correct ID and type the following: xen-hvmcrash <ID> (without the brackets). 

Congratulations, You have now successfully crashed the Virtual Machine!

Automate tasks with use of XenServer Powershell Module

Working with backups of your virtual machines is obviously essential. Working with exports in XenServer can some times be time consuming, particularly with bigger virtual disks attached to your virtual machine. In this scenario I will show you an alternative to manually export via XenCenter, by doing it with Powershell to an remote server using XenServer Powershell module.

XenServer Hotfix XS70E004 viktig vid installation av XenServer 7.0

Vid installation av och uppgradering till XenServer 7.0 finns det en överhängande risk att data på anslutna SR blir korrupt. Citrix rekommenderar därför inte bara installation av hotfix XS70E004 som löser problemet utan skriver till och med att alla som har installerat XenServer 7.0 måste installera hotfixen.

Länk till nämnd hotfix:

Se till att hålla er XenServer-miljö uppdaterat enligt Citrix lista på rekommenderade hotfixar för Xenserver: