On behalf of the entire XenServer product team at Citrix, I’m pleased to announce general availability of the XenServer 6.0 release.

As the “6.0” naming implies, this is a MAJOR new release of the product.  Here’s a look at what’s new:

Architectural Changes

  • The Boston release is based on the open-source Xen 4.1 hypervisor.   XenServer is another commercial product to ship with the Xen 4 hypervisor.  For those of you who like to follow the open source world, Oracle VM 3 launched a few weeks ago, and is based on the Xen 4 hypervisor.  Ubuntu Server 11.10 will soon follow with support for Xen 4, and will be the Linux distro to benefit from Xen being included in Linux 3.0.
  • The Open vSwitch (OVS) is now the default network stack for the product.  OVS was first introduced in XS 5.6 FP1 as a post-install configuration option, and is the basis for the distributed virtual networking (DVS) features like NetFlow, RSPAN and security ACLs, as well as NIC bonding improvements and Jumbo frames support.  Improvements to DVS include improved availability through the “fail-safe” option, as well various improvements based on customer feedback from XenServer 5.6 FP1.  Note that the legacy Linux bridging stack is still available via a post-install configuration option, for those that need it.
  • While the DVS features are interesting, the most strategic aspect of OVS in XenServer is how it enables next-generation Cloud environments to be built with OpenFlow network standards.  This is yet another reason why XenServer is winning in the Cloud.  Reference the cloud services from vendors such as Rackspace, Zynga, GoDaddy, and Softlayer (just to name a few)–all of which are powered by XenServer.
  • Support for hardware-assisted (SR-IOV) network performance optimization has been improved, particularly for use with the NetScaler VPX and SDX products.  A future version of NetScaler SDX will ship with XenServer 6.0 onboard.

Product simplification.

We’ve done a number of things to make the product even easier to deploy and manage.  These include:

  • We have simplified the management infrastructure requirements for features such as Workload Balancing, StorageLink, and Site Recovery.  In fact, for StorageLink and Site Recovery, no additional management infrastructure is required at all.
  • Workload Balancing (and the historical reporting features which rely on its database) is available as a Linux-based virtual appliance for easy installation and management.
  • The Linux supplemental pack has been removed, so there is only 1 base installation CD.  “Linux demo VM” functionality has been moved to a virtual appliance format so it can be easily imported into a host or resource pool.

Virtual Appliance and V2V improvements

  • Virtual Appliance support.  Within XenCenter you can create multi-VM virtual appliances (vApps), with relationships between the VMs for use with the boot sequence during Site Recovery.  vApps can be easily imported and exported using the Open Virtualization Format (OVF) standard.
  • VMDK and VHD import functionality is integrated into XenCenter for interoperability with VMware VMDK and Microsoft VHD disk images.  Reliability of the “transfer VM” used for appliance import/export has been improved.

Microsoft System Center integration

  • Starting with the 6.0 release, you will have the option of managing XenServer hosts and VMs with System Center Virtual Machine Manager (VMM) 2012.  For more information refer to the Microsoft System Center 2012 beta page.
  • System Center Operations Manager 2012 will be able to manage and monitor XenServer hosts and virtual machines.
  • System Center integration is available with a special supplemental pack (“Integration Suite Supplemental Pack”) from Citrix.


  • Boston is the first XenServer release to include HDX enhancements for optimized user experience with virtual desktops.
  • With the Boston release, a physical GPU can be assigned to a VM so the applications running in the guest can leverage GPU instructions (“GPU pass-thru”).  This provides significant TCO benefits (over prior alternatives such as Blade PCs) for the XenDesktop HDX 3D Pro technology used for delivery of CAD and other graphical applications via virtual desktops.

Guest OS support updates

  • Formal guest support for Ubuntu 10.04
  • Updates for support of RHEL 5.6, Oracle Enterprise Linux 5.6, Oracle Enterprise Linux 6.0, CentOS 5.6, and SLES 10 SP4
  • Experimental VM templates for Ubuntu 10.10, CentOS 6.0, and Solaris
  • Note also that RHEL 6.0 and Debian Squeeze are fully supported (these are also supported with XS 5.6 SP2)

Performance Improvements

  • XenServer 6.0 will ship on-board a future version of NetScaler SDX, which uses XenServer’s SR-IOV enhancements to drive line-speed (up to 10 Gbps) performance to virtual machines
  • Host (dom0) network throughput has been increased by 70-100%
  • Improved XenMotion performance, especially as compared to XenServer 5.6.0.

Other enhancements and improvements

  • A “rolling pool upgrade” wizard is provided in XenCenter to enable easier upgrades from 5.6.x.  Using the HTTP/FTP/NFS media options you can run fully “hands off” upgrades remotely.
  • High Availability (HA) permits configuration of a boot sequence for recovery, as well as storage of the heartbeat disk on NFS.
  • Host RAM support has been increased to 1 TB.
  • VM vCPU and vRAM support is increased e.g. up to 16 vCPUs and 128 GB RAM for Windows; increased Linux vCPU and vRAM support levels vary by distro (see the VM installation guide for more information).
  • NIC bonding improvements, including more formal support for active/passive mode
  • XenCenter will be localized into Japanese and Simplified Chinese (these will be generally available a few months following the English release)

Noteworthy changes to existing features

  • VM Protection and Recovery is now included in Advanced, Enterprise, and Platinum editions.
  • StorageLink: With the move from the Windows-based “StorageLink Gateway” to “integrated StorageLink,” some StorageLink array support is being retired.  Arrays whose StorageLink supportability is being retired will continue to be supported via the standard iSCSI and Hardware HBA Storage Repositories.  Focus for StorageLink support is being placed on arrays with standards-based SMI-S interfaces (e.g. EMC CLARiiON) and those which are widely used with XenServer (NetApp and Dell EqualLogic).  StorageLink Gateway will continue to be supported with XenServer 5.x until September 2013 according to the lifecycle policy posted here.   Note also that the new “rolling pool” upgrade takes care of upgrading from StorageLink Gateway, and performing validation for unsupported arrays.
  • Site Recovery:  Site Recovery is no longer based on StorageLink.  The new “integrated” Site Recovery feature enables DR support for virtually any iSCSI or Hardware HBA storage repository where the underlying array includes replication features (either supplied by the array vendor or a third-party replication scenario).
  • XenConvert 2.4. XenConvert is now purely a P2V tool.  As mentioned before, V2V functionality is now integrated into XenCenter.

What happened to Self-Service Manager?

  • The short answer: We are not making the Self-Service Manager feature (which we had made available during the 6.0 beta) available at this time.
  • The longer explanation: Citrix recently acquired Cloud.com–specifically the CloudStack and Cloud Portal products–which immediately required us to re-assess the plans on the Self-Service Manager feature.  The CloudStack and Cloud Portal products are focused on enabling customers to build and manage cloud environments.
  • Over time, the plan is to focus future 100% of our development efforts on CloudStack and Cloud Portal as the underlying technology for cloud management and self-service of virtualized environments.
  • While we did see a lot of interest in the Self-Service Manager feature during the beta period, we did not want to release Self-Service Manager knowing full well that it would not receive the long-term attention for ongoing development that customers would expect.
  • The “Web Self-Service” simple web-based admin tool, first introduced in XenServer 5.6 FP1, is still available with XenServer 6.0

Product Naming / numbering scheme

For a variety of reasons, we’re no longer going to use the “Service Pack” and “Feature Pack” nomenclature for XenServer, and will go strictly with a x.y.z numbering scheme.  So 6.0 is actually “6.0.0.”  Here is how we will name/number future releases* we are currently working on:

  • 6.0.1 is reserved for a possible non-retail release of XS used by an upcoming version of the NetScaler SDX product
  • 6.0.2 is planned as the hotfix rollup + maintenance release post-6.0, targeted for Q1 2012.  (This would be the release to target if you are the type who likes to wait for “Service Pack 1” for major releases)
  • 6.1.0 is planned as a new feature release in mid-2012
  • 6.1.1 is planned as the XenServer release to ship with an upcoming major version of XenDesktop, with even more useful features for XenDesktop and XenApp.
  • 6.5.0 is planned as the next “Major” release, where we aim to do things like upgrade the Dom0 OS, integrate the new version of the Xen hypervisor, and add a number of new features.

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*Disclaimer: The development, release and timing of any features or functionality described for our products remains at our sole discretion and is subject to change without notice or consultation. The information provided is for informational purposes only and is not a commitment, promise or legal obligation to deliver any material, code or functionality and should not be relied upon in making purchasing decisions or incorporated into any contract.