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Citrix XenServer 6.5

Citrix XenServer 6.5

Citrix have released a major release of their hypervisor XenServer 6.5

I have with this blogpost gathered all the public informations available and created a blogpost on what I think is new with Citrix XenServer 6.5 and why this is great and how you can use this.

FAQ on how Citrix XenServer is used in the world and how its changing the world.

Its the industry-leading fully open source virtualization platform that supports cloud, datacenter and desktop virtualization infrastructures. XenServer is used for 40% of Citrix XenDesktop deployments and 60% of Citrix CloudPlatform deployments. XenServer is the power behind the great product Citrix NetScaler SDX. 750.000+hosts are running Citrix XenServer around the world. XenServer is running the worlds largest public and private clouds and its powered by Xen Project hypervisor. It have been the prefered hypervisor used for GPU pass-through or vGPU solutions. Citrix XenServer helped NVIDIA change the market for GPU cloud, datacenter and desktop virtualization with colloborating their NVIDIA GRID which lower the price of GPU’s that can be virtualized and give a better EUC experience.

Raw facts.. have it been worth waiting for XenServer 6.5

Lets face it, last version was in 2013, now its 2015 and is it worth waiting for next version of version 6.5. Yes it is why, cause now Dom0 have been upgraded from 32bit to 64bit, this means performance is boosted big time since version 6.2. Hypervisor is upgarded to Xen 4.4 in Citrix XenServer 6.5 and 64 bit domain0 (Dom0) can handle more VM’s, more data, 50% increase in GPU density with NVIDIA GRID vGPU profiles, better support for new CPU’s from Intel and AMD such as Intel Haswell EP and AMD Warsaw + much more

Look at this sample of benchmarks comparing the performance of Citrix XenServer 6.2 vs Citrix XenServer 6.5


Pretty impressive, looks like 64bit with Dom0 have improved the XenServer big time, lets dig in the features.

New Features and Improvements in XenServer 6.5

Citrix XenServer continues to be a fundamental platform for Citrix’s long term goal of enabling work and play from anywhere, from any device. With the introduction of XenServer 6.5, Citrix delivers support for the newest 64-bit hardware and latest Guest operating systems, delivering increased vGPU scalability, in-memory read caching and performance improvements in the areas of storage and networking.

Architectural Improvements

Citrix XenServer 6.5 introduces many architectural improvements which aim to improve overall performance and removes a number of scalability limitations in XenServer 6.2. For details of the new configuration limits, refer to CTX141510 – XenServer 6.5

Configuration Limits.

Citrix XenServer 6.5 – Virtual Machine (VM) Limits

Virtual Machine (VM) Limits 2015-01-13_0828

Citrix XenServer 6.5 – Host Limits

xenserver 65 host limits
Citrix XenServer 6.5 limits

64-bit Control Domain Linux Kernel

The new 64-bit Control Domain (Dom0) enables XenServer to accommodate many more PCI devices per host (NICs, GPUs, and so on), and allows the use of devices that are 64-bit only (including many Solid State Drive solutions). The new 64-bit kernel removes the previous restrictive low/highmemory division which limited the maximum amount of memory that Dom0 could use. This could
result in sub-optimal memory performance within Dom0, when more than 752MB RAM was allocated. In addition, Dom0 has been upgraded from CentOS 5.7 to CentOS 5.10.

Dom0 memory is automatically configured depending on the amount of free host memory and can be scaled and optimized to cope with memory demands of the very latest vGPU, disk and network drivers. This enables support for more Virtual Machines (VMs) and internal caches to speed up disk access

New Xen Project Hypervisor v4.4

XenServer 6.5 includes the latest Xen Project hypervisor available; v4.4 delivers many improvements.
It vastly increases the number of virtual event channels available for Dom0, from 1023 to 131071,
which translates into a correspondingly larger number of attached virtual devices. XenServer v6.2 used a special interim solution that provided 4096 event channels, which was enough for around
500 VMs per host but with only a few virtual devices in each Virtual Machine. With the support for
extra event channels in version 4.4, XenServer 6.5 allows each of these VMs a far richer set of virtual
devices. Xen 4.4 also handles grant-copy locking requests more efficiently, dramatically improving
aggregate network and disk throughput.

In-memory Read Caching

In scenarios where golden images are deployed and VMs share much of their data, the few specific blocks VMs write are stored in differencing-disks unique to each VM. Read caching improves a VM’s disk performance as, after the initial read from external disk, data is cached within the XenServer host’s memory. This enables all VMs to benefit from in-memory access to the contents of the golden image, reducingthe amount of I/O going to and from physical storage. It greatly improves performance in situations where many VMs are cloned off a single base VM on a read-caching supported SR (currently EXT and NFS). For example, in XenDesktop Machine Creation Service (MCS) environments, it drastically reduces the number of blocks read from disk. This performance improvement can be seen whenever data needs to be read from disk more than once. This is most pronounced in the degradation of service that can occur during heavy I/O situations. For example, when a significant number of end users boot up within a very narrow time frame (boot storm), or when a significant number of VMs are scheduled to run malware scans at the same time (anti-virus storms).

** keep in mind this features is only available XenServer 6.5 Desktop+ License edition or its called if you are a Citrix XenDesktop Platinum customer.



Storage Improvements

There are several improvements, including the ability for XenServer to free up previously used blocks from a LUN (i.e. deleted VMs from an SR), live LUN expansion, support for tapdisk3 and an updated device mapper multipath

Network Improvements

There’s an updated Open vSwitch (now at v2.1.3), GRO is enabled by default and now a Netback Thread per VIF, which is an improved way of sharing resources and improving performance with para-virtualized VM NICs.  There is also an updated DVSC, the distributed virtual switch controller with a number of platform related security fixes. Improved IPv6 guest performance.

New Guest Operating Systems support

  • Ubunto 14.04
  •  & SLES 12
  • Debian 7.2 “Jessie”
  • CentOS 5.10,6.5,7.0
  • Red Hat 5.10, 6.5, 7.0
  • Oracle Linux 5.10, 6.x
  • Oracle UEK 6.x

Workload Balancing

Workload Balancing appliance is back..

  • Reintroduction of Workload Balancing appliance
  • Generate performance monitoring reports
  • Alert administator to system hot spots
  • Automatically place workload based on historic data
  • Dynamically move workload based on CPU, storage & network load

** keep in mind this features is only available XenServer 6.5 Enterprise & Desktop+ License edition or its called if you are a Citrix XenDesktop Platinum customer.

XenCenter Improvements

  • XC Logs and Alerts rewrite
  • Hotfix notification process improved
  • Settings of cores per socket via GUI
  • DVSC fully supported, no longer shown as deprecated
  • XC installer improved including slimmed down .NET install

NVIDIA GRID vGPU improvements- support up to 96 vGPU profiles pr host

Citrix XenServer has led the market in its support for virtualized graphics processors.  GPU passthrough has been around for a while and even some of our competitors also feature it, however it was never a scalable solution for large volumes of desktop virtualization users.  vGPU, introduced a year ago by Citrix with Support for NVIDIA GRID cards meant suddenly, higher numbers of users could get access to advanced graphics in a virtualized desktop scenario.

In this release, Citrix scaled their support for vGPU sessions by 50%, now with 96 vGPU sessions per host.  Obviously you need to have the appropriate h/w host to support 3 NVIDIA GRID cards, with all necessary resources to run the numbers of VM, however, it demonstrates how Citrix continues to lead the market for organizations seeking application and desktop virtualization solutions. Remember when you add more GRID cards in a server its recommended having the more CPU for this.

** keep in mind this features is only available XenServer 6.5 Enterprise & Desktop & Desktop+ License edition.

*** Keep in mind NVIDIA GRID vGPU is not available in the free version or standard version of Citrix XenServer

**** GPU pass-through feature is available for all versions for Citrix XenServer 6.5 including the free edition.


Citrix XenServer 6.5 License FAQ

Citrix XenServer 6.5 is available in 1 free edition & 4 commercial editions:

Commercial editions

  • Standard
  • Enterprise
  • Desktop
  • Desktop+

The Standard edition is Citrix entry level commercial offering, with a range of features that will suit the needs of those customers who want a robust and high performing virtualization platform, but do not require the premium features offered by the Enterprise edition; while still wishing to benefit from the assurance of comprehensive Citrix support and maintenance.

The Enterprise edition is Citrix premium offering, optimized for both server, desktop and cloud workloads. In addition to the Standard edition, it offers access to in-memory read caching, Dynamic Workload Balancing, GPU Virtualization (vGPU) with NVIDIA GRID, VMware vSphere to XenServer Conversion utilities, Intel Secure Measured Boot (TXT) and Export Resource Data.

The Desktop edition is only available to customers who have purchased XenApp or XenDesktop; it includes all XenServer features previously available to XenApp or XenDesktop customers. This includes features that the Standard edition does not have, namely: Dynamic Workload Balancing, GPU Virtualization (vGPU) with NVIDIA GRID, VMware vSphere to XenServer Conversion utilities, Intel Secure Measured Boot (TXT), as well as full Citrix support and maintenance.

The Desktop+ edition is only available to customers who have purchased the Platinum edition of XenApp or XenDesktop; in addition to the features available in the Desktop edition, it also includes access to in-memory read caching.
Note: Upgrades to the Enterprise edition are available from the Standard edition. To buy a XenServer 6.5 license, click here.

In XenServer 6.5, customers should allocate product licenses using a Citrix License Server, as with other Citrix components. From version 6.2.0 onwards, XenServer (other than via the XenDesktop licenses) is licensed on a per-socket basis. Allocation of licenses is managed centrally and enforced by a standalone Citrix License Server, physical or virtual, in the environment. After applying a per-socket license, XenServer will display as Citrix XenServer Per-Socket Edition.
Note: Mixed pools of licensed and unlicensed hosts will behave as if all hosts were unlicensed.

Read more about the Citrix XenServer 6.5 License FAQ here

Citrix XenServer Feature Set 6.1, 6.2 vs 6.5

Below graph give a great overview which feature is available for the free version vs the paid version in XenServer 6.5
The feature set gives also a great overview what is new in XenServer 6.5 compared to 6.1 & 6.2
* hint click the image for larger picture to see better the details.

xenserver feature set


Download Citrix XenServer 6.5 media here

Download Citrix XenServer 6.5 installation guide here

Download Citrix XenServer 6.5 graphics guide here (used if you want to configure GPU pass-through or NVIDIA vGPU)

Download  Citrix Xenserver 6.5 Technical FAQ

Download Citrix XenServer 6.5 Configuration Limits

Download Citrix XenServer 6.5 Release Notes

Download Citrix XenServer 6.5 Admistration Guide 

Download Citrix XenServer 6.5 Virtual Machine User Guide

Download Citrix XenServer 6.5 Management API Guide

Download Citrix XenServer 6.5 Workload Balancing Quick Start Guide

Download Citrix XenServer 6.56 Workload Balancing Administrator’s Guide

Download Citrix XenServer 6.5 vSwitch Controller User Guide

thomas poppelgaard CTP & MVP

Citrix technology professional – CTP, and Microsoft Most Valuable Professional MVP, Thomas Poppelgaard provides professional services. Write to me on my email or call on my cell +45 53540356

Citrix XenDesktop, Citrix XenServer, testing, user experiance, VDI, vGPU 352.83-354.80, virtual reality, xenserver 6.5

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