Citrix XenServer

• Citrix XenServer is the platform for server virtualization and management of a hypervisor.
• Citrix XenApp and XenDesktop - the complete solution for delivery of virtual applications and desktops, Delivery of Windows applications, Linux, web applications and applications of SaaS or completely virtual desktops to workers to any place, on any device. Can work with the systems of virtualization Citrix XenServer, VMware vSphere or Microsoft Hyper-V.

2017: Citrix XenServer 7.x is certified by FSTEC

At the beginning of 2017 the certificate of conformity of FSTEC of Russia No. 3693 on the Citrix XenServer 7.x virtualization platform is received. Certification tests of a software package lasted 9 months and were carried out on compliance to requirements of specifications. Citrix XenServer 7.x represents the checked solution of a corporate class for virtualization of servers and workstations. The certificate of conformity confirms that the Software package XenServer is intended for the data protection of limited access which is not containing the data which are the state secret in the state information systems 3 and 4 of a class of security and also for providing 3, 4 levels of security of personal data in information systems for which threats of the 3rd type are referred to relevant.

Being the virtualization platform, the certified software package Citrix XenServer 7.x. will become excellent addition to the solution for virtualization of desktops and the Citrix XenDesktop 7.x applications certified earlier. It should be noted what for Citrix XenDesktop was indicated in requirements to the functioning environment on the need of use of the certified hypervisor. Now this requirement became even easier to be fulfilled after a release of the certificate to XenServer, quite often it is convenient to clients to buy solutions of one vendor: it allows to weaken financial loading and not to worry on compatibility of solutions.

In spite of the fact that for Citrix XenServer 7.x there are open codes, control of lack of not declared opportunities within certification was not carried out. "Of course, we understand that certification with check of absence of NDV corresponds to higher class of security and gives to the customer more opportunities, in particular, at certification of the information systems. But at the same time it is frequent in view of complexity and duration of the procedure of inspection control with verification of the code, clients will be forced to expect long an exit of security updates that from our point of view, is more critical for the client within operation of solutions of Citrix" — the chief engineer of representative office of Citrix in Russia and the CIS countries Halyapin Sergey.

2016: Citrix XenServer "Dundee" Tech Preview 3

On March 14, 2016 it became known of an exit of the third the beta of new generation of this product - XenServer Dundee of TP3^[1].

The most important functions which were a part of XenServer Dundee of TP3:

• Installation of drivers of devices of input-output through the Center of updating Windows.
• Support of acceleration of graphics means of Intel GVT Virtual GPU for Windows.
• Improvements of hardware acceleration of graphics with support of NVIDIA GRID 2.0.
• Support of SMB storages as the general storage (repository) for VM on XenServer.
• Performance improvements due to support of AVX and AVX2.
• Expanded support of means of scaling allows to add new nodes to the existing pools of resources, irrespective of processor type (provided that they the same producer). Now virtual machines can easily migrate between pools.
• Loading on program iSCSI for architecture of Cisco UCS.
• Funds of migration from the VMware vSphere platform (including version 6.0) at the expense of the solution XenServer Conversion Manager.
• Functionality of balancing of workload (Workload Balancing).
• Improvements of scalability and performance:
  • Support up to 5 TB RAM on a host
  • Support up to 1.5 TB RAM of the virtual machine
  • Supports up to 288 physical processors
  • Support up to 32 virtual processors of virtual machines (vCPU)
  • Support up to 255 VBD (Virtual Block Device) for the virtual machine
  • Support up to 4096 VBD (Virtual Block Device) per host server

For March 15, 2016 Citrix XenServer Beta 3 is available to the acting clients with the commercial license XenDesktop or XenApp. The license key is required and it is activated by means of Citrix License Server.

2015

Citrix XenServer 6.5 Creedence

In January, 2015 the Citrix company announced release of upgraded version of the server platform of virtualization of Citrix XenServer 6.5 (the code name Creedence):

• 64-bit domain dom0 (i.e., now all 64-bit)
• New version of a core of Linux 3.10
• Hypervisor of Xen of version 4.4
• The Workload balancing (WLB) functions provided by the separate virtual module WLB appliance
• The updated virtual switchboard Open virtual switch 2.1.x
• Distributed Virtual Switch Controller (DVSC) component
• Full support of vGPU technology for VDI Wednesday (up to 96 vGPU per host)
• Improvements of processing of the phenomenon of Boot storm using use of a cache on reading
• Use of In-memory read caching for repositories of storages of file type
• Use the technician of TRIM and UNMAP for return of disk tanks on the party of storages during removal of virtual machines
• Migration of virtual machines from the 32-bit platform on 64-bit
• Technology of migration of storages with XenServer 6.2 and earlier
• Numerous performance improvements
• The new most supported configurations (is more detailed here)
• Support of guest SLES 11 SP3 and Ubuntu 14.04 LTS OS

In addition to the XenServer Standard edition appeared Enterprise Edition. Only in the last there are following components and technologies:

• In-memory read-cache
• Dynamic resource scheduling (workload balancing)
• Safe loading of the platform of a hypervisor (Intel of TXT)
• vSphere workload conversion manager

XenServer supports Intel Trusted Execution technology (Intel of TXT) which monitors unauthorized use of a hypervisor, without giving the chance to applications to work on potentially compromised machine. Innovation in this release of the platform is function of marking of resources which implements a geobinding of workloads. It gives the chance to limit accomplishment of loadings in a certain place from security reasons. The XenServer platform expands the functionality of virtualization of the graphic processor leading in the industry even more, supporting Nvidia Grid vGPU technology; besides, the platform provides increase in density of three-dimensional graphic applications of the high level on virtual desktops on the server for 50%. Thanks to architecture of a kernel of OS of new generation which supports an opportunity and a corporate and operator class XenServer represents the most complex and economic virtualization platform with the open code which will be ideal for both the different companies, and service providers.

To conform to the growing requirements of a segment of mobile corporations, the technology of cloud infrastructure which as much as possible and safely increases flexibility and efficiency of both working environments of end users, and data processing centers is necessary for customers. XenServer is the main center of this cloud infrastructure on the basis of which crucial workloads of large world service providers and cloud services are executed. For example, 50% of the implemented products XenDesktop work based on XenServer. Advantages of new technology to corporations and service providers consist in efficiency and flexibility which are reached thanks to reliable and fast accomplishment of large volumes of the new and existing loadings. Also the efficiency of IT systems thanks to high utilization coefficients and consolidation of infrastructure and also decrease in the total operational cost of DPC reached due to increase and optimization of use of infrastructure and computing powers increases.

The architecture provides the improved performance

As a result of use new 64 bit architecture of a core of XenServer significant increase in performance of work of networks and data warehouses was reached that provided customers with the powerful virtualization platform for accomplishment of the new and existing workloads in working environments and DPC. As a part of new release of the platform possibilities of balancing of workloads (WLB) and the controller of the distributed virtual switchboard (DVSC) were also provided. This new functionality does XenServer by the most important component of the biggest and complex cloud systems in the world.

Virtualization of the graphic processor integrates with NVIDIA GRID vGPU technology

The XenServer platform is the virtualization platform of a corporate and operator class with the open code which provides high-scalable support of NVIDIA GRID vGPU technology at virtualization of the graphic processor and also natural integration of a cloud for CloudPlatform and other not proprietary platforms of management of cloud resources. Thanks to increase in density of virtual machines by 50%, customers the using XenDesktop and XenApp technologies using which functioning of three-dimensional graphic applications of the high level is ensured receive bo'lshy quantity of desktops using XenServer counting on 1 physical server. As a result of it it is possible to reduce considerably costs and to improve functionality for end users.

"Representing the latest version of the XenServer 6.5 platform the Citrix company offers the customers a significant change in performance and increase in density of the virtual machines using three-dimensional graphics for 50%. XenServer is one of unique solutions with the open code for the companies of the different directions around the world. Now Citrix provides the cloud infrastructures necessary for the companies for the most complete use of potential of modern applications within complex product assortment which can be used for creation of cloud resources in open network of an operator class taking into account their cost efficiency", – Halyapin Sergey, the head of department of the Citrix system engineers in Russia and the CIS countries comments on news.

2014

Preliminary release of Citrix XenServer

On July 25, 2014 the Citrix company announced release of preliminary technology release of the new version of XenServer. The version number of a product is not specified.

The updated possibilities of XenServer

• 64-bit domain dom0
• New version of a core of Linux 3.10 kernel
• The updated virtual switchboard Open virtual switch 2.1.1
• Processing of the phenomenon of Boot storm using use of a cache when reading is improved
• Read caching for repositories of storages of file type is used
• Use the technician of TRIM and UNMAP for return of disk tanks on the party of storages during removal of virtual machines
• Migration of virtual machines from the 32-bit platform on 64-bit
• Technology of migration of storages with XenServer 6.2 and earlier
• Support of guest SLES 11 SP3 OS
• Support of guest Ubuntu 14.04 LTS OS

2013

XenServer 6.2 -> Open Source

The Citrix company announced on July 9, 2013 - XenServer hypervisor, since the latest version 6.2, passes into discharge of Open Source. The vendor creates the new XenServer.org portal for developers and partners who will be able to continue to develop this product.

XenServer returns to sources, noted in media. A basis of this product - Xen hypervisor created at the Cambridge university in 2003 and extended on the Open Source model. In 2007 Citrix purchased Xen for $500 million, at the same time left its core open. Supplementing Xen with the patented code, the company called the final solution XenServer.

Almost all functionality of XenServer becomes open and free. XenServer will be able to use the companies creating the public or private clouds wishing to receive for this purpose the free or inexpensive solution having the developed functionality necessary for implementation of such plans.

It is supposed that XenServer will be able to be integrated with the CloudStack system intended for creation, deployment of "clouds" and management by them. Citrix purchased CloudStack in 2011, and in 2012 transferred it to the Apache Foundation organization for promotion for the Open Source model.

Relatives will not approach

Development of Xen and XenServer seems to developers separate. The Linux Foundation organization, and for the second — XenServer.org is responsible for the first. The product XenServer will still use as Xen core and also to include management tools a hypervisor of XenCenter and other tools. XenServer and XenCenter will extend according to the licenses GPL, BSD and Citrix. Instead of different editions XenServer, there will be now an only option for which support Citrix offers paid services.

Not touch giants

Competing with VMware and Red Hat, the Citrix company tries not to touch Microsoft which advances hypervisors of Hyper-V and ESXi. So, according to representatives of Citrix, XenServer is intended not for all infrastructures, and mainly for cloud. The company notes that clouds are absolutely new and novel area, and the price of a hypervisor has huge value for their creators.

The version of XenServer 6.2 includes a number of innovations among which there are an expanded horizontal scalability and the increased performance, support Windows 8 and Windows Server 2012, integration with means of virtualization of desktops XenDesktop.

Citrix XenServer 6.2 Service Pack 1

On December 13, 2013 the Citrix company released Service Pack 1 for the XenServer 6.2 virtualization platform.

In addition to adjusting "patches" in the solution the set of new features is stated, in particular:

• Full support 3D - diagrams for NVIDIA GRID GPU.
• Improvements of the mode of a direct probros of the graphic module (GPU pass-through).
• Support of guest OS Windows 8.1 and Windows Server 2012 R2.
• Improvements of the master of Site Recovery for ensuring big installation of the solution (connection of a large number of FC LUN).
• Support of creation up to 50 new HBA SR devices at deployment.
• Improvements in a security system.

Citrix XenServer 6.2 includes only 2 editions: paid and free. Without separation of Advanced, Enterprise, Platinum.

Functionally, these two versions absolutely identical and all opportunities what are in the paid version, is also in free. The released Citrix updating \Service Packs, etc. are applicable both to paid and to the free version. (are downloaded from the website)

Difference of the paid version from free:

• Support from Citrix is included in the price of the paid version: customers can get technical cases in the world support service in case of any failure or a question.
• Possibility of installation of updates, using the graphical interface of the management console CitrixXenCenter. In the free version of updating can be set only via the command line interface.

Citrix XenServer 6.2 is licensed by the number of processor slots in the server: i.e. in the 2nd the processor server it is necessary to purchase 2 licenses.

Support of NVIDIA GRID is implemented

On October 1, 2013 the Citrix Systems company announced support implementation by the Citrix XenServer platform of NVIDIA GRID technology. The official release of support of technology matched release of XenDesktop 7.1.

Using XenServer hardware GPU sharing technology (it is supported in XenServer 6.2) there is available a use of virtual graphics adapters (vGPU) in the virtual machines directly using resources of the special hardware from NVIDIA and performing intensive processing 3D - diagrams. The equipment not of all vendors is compatible to this technology.

The NVIDIA GRID technology is available both to Citrix XenServer, and to VMware vSphere/ESXi (a basis of the VDI solution VMware View), however Citrix announced use of "native" drivers of NVIDIA while VMware applies own:

Restriction of functionality of the vSGA and vDGA modes at VMware vSphere was expressed so:

The vGPU technology from Citrix works only for guest OS so far Windows 7 and Windows Server 2008 R2 therefore to try it from new Windows 8.1 will not leave.

2011

Citrix XenServer 6.0

The Citrix company officially began deliveries of the complex XenServer 6.0 virtualization platform in September, 2011. Among the main differences it is possible to note the improved means of disaster recovery for data protection and also failure from a binding to the Windows operating system at full-scale recovery of distributed systems. The Integrated Site Recovery technology which succeeded former StorageLink Gateway DR technology for the first time offers remote replication of data between disk arrays with functions of the accelerated recovery and switching to the recovered resources.

Though Citrix and Microsoft companies save the closest partnership in technology and marketing aspects, XenServer 6.0 shows some withdrawal from a binding to Windows in key technologies for ensuring fault tolerance. For large-scale vosstanovleniye in distributed system it is not necessary to use the virtual machine running Windows any more. Also virtual Windows machine is not required for access to such functions of storages now as replication of data, deduplication, creation of pictures and cloning. New tools for load distribution it is constructed based on virtual by Linux machine which not only consumes less resources, than the virtual device based on Windows, but also allows to refuse acquisition of additional licenses for Windows.

One of examples of cooperation increase of Citrix and Microsoft is the ability to integrate XenServer 6.0 with the complex platform of management of Microsoft System Center VMM (Virtual Machine Manager) 2012. Though the Citrix company itself already provides management tools for Microsoft Hyper-V hypervisor, VMM 2012 existing in the form of the beta will be able to control a host servers and XenServer virtual machines, and further the same access will be got also by the System Center Operations Manager 2012 platform. The Citrix company notes that such integration is available only to XenServer 6.0 and is not supported in the previous versions.

In notes to XenServer release 6.0 developers noted about 20 new and improved features, including enhanced capabilities of import of virtual machines and devices from environments of VMware. From other innovations It should be noted support to 1 Tb of RAM on the physical XenServer server and also up to 16 virtual processors and 128 GB of memory in virtual machines. Were included in the expanded list of the supported guest systems such Linux distribution kits as Ubuntu, CentOS, Solaris and Oracle Enterprise Linux. Considering traditional attention of Citrix to virtualization of desktops, it should be noted improvements in support of graphics of high resolution and hardware acceleration using graphic processors.

Developers announced some problems with access to disks through network channels of standard 10 Gigabit Ethernet, interruptions in loading of virtual Windows machines at stream delivery through service Citrix Provisioning Services and also incorrect calculation of the place taken by virtual disks.

List of new opportunities of Citrix XenServer 6.0:

• Integrated Site Recovery (Disaster Recovery) is replication of the fast recovery and failback technologies given on the remote platform with support. The Integrated Site Recovery function replaces the predecessor - StorageLink Gateway Site Recovery ispolzuyuemy in the previous versions. Now need is unavailable separate service VM with Windows.
• Integrated StorageLink is a possibility of direct access to functions of the disk array, such as replication, deduplication of the data, snapshots and clones (executed by means of an array). Function appeared instead of StorageLink Gateway and, besides, does not require service VM with Windows.
• GPU Pass-Through - allows to route live video adapter resources in the virtual machine (support both single GPU card, and multi-card GPU card). It will allow to improve performance of a graphic subsystem in installations of XenDesktop VDI with 3D Pro HDX technology.
• Virtual Appliance Support (vApp) - all virtual modules (virtual appliances) are constructed based on Linux now and are delivered in the corresponding Open Virtualization Format (OVF) formats. There was an opportunity to create multimachine configurations (virtual service - vApp) which can be integrated with Integrated Site Recovery and High Availability technologies.
• Rolling Pool Upgrade Wizard - the master of "Rolling Pool Upgrade" simplifies updates a host servers (an automatic or semi-automatic mode) at the expense of a preproverka of requirements to updates and step-by-step updating.
• Microsoft SCVMM & SCOM Support is management of hosts of XenServer and virtual machines from System Center Virtual Machine Manager (VMM) 2012. Also monitoring of XenServer using System Center Operations Manager 2012 on which the special packet from Citrix is rolled is supported. More detailed information here: Microsoft System Center 2012 Virtual Machine Manager page.
• Distributed Virtual Switch Improvements - the new mode "fail safe mode" allowing to create virtual private networks between several a host servers, support of the access lists ACL, the scheduler of QoS, the RSPAN and NetFlow settings.
• Increased Performance and Scale is support up to 1 TB memories of a host of XenServer hosts, up to 16 virtual processors of machines and 128 GB of memory for the virtual machine. XenServer Tools which have the smaller size are also improved.
• Networking Improvements - the Open vSwitch device is a network stack by default in XenServer 6.0 now and allows to create groups of Active-Backup NIC bonding adapters.
• VM Import & Export Improvements - import of virtual modules directly from XenCenter with opportunities to change settings of the virtual machine (virtual processor, virtual memory, virtual interfaces and a repository of storage). Full support of means of XenConvert and import of virtual machines of VMware.
• SR-IOV Improvements is support of SR-IOV technology and certification with a packet of SR-IOV Test Kit. Experimental support of SR-IOV with hot migration of XenMotion for Solarflare adapters.
• Simplified Installer - the software installer a host server requires only one ISO image.
• Enhanced Guest OS Support is support of guest Ubuntu OS 10.04 (32/64-bit), Debian Squeeze 6.0 64-bit, Oracle Enterprise Linux 6.0 (32/64-bit) and SLES 10 SP4 (32/64-bit). The VM experimental templates for CentOS 6.0 (32/64-bit), Ubuntu 10.10 (32/64-bit) and Solaris 10.
• Workload Balancing Improvements is the new virtual module of the balancer based on Linux instead of the module based on Windows.
• XenDesktop Enhancements is improvements of HDX technology for VDI installations.
• VM Protection & Recovery - this function is available to the Advanced, Enterprise and Platinum Edition editions now (i.e., to all paid).
• NFS Support for High Availability - as HA Heartbeat disk can be used now NFS storage, respectively for these storages technologies of fault tolerance work.
• XenCenter Improvements - the transactions XenCenter are executed in parallel now.
• Host Architectural Improvements - XenServer 6.0 is constructed based on a hypervisor of Xen 4.1 with support of GPT and improvement

Citrix XenServer 6.1

• The improved integration with cloud platforms - Citrix made a set of improvements for cloud infrastructure of Apache CloudStack and Citrix CloudPlatform (based on the same Apache CloudStack), including the improved management tools the network screen, balancing of loading of Source Load Balancing (SLB) and also security and an intrusion prevention. There was a support of LACP 802.3ad, a timing of 4 NIC in the active/active configuration and also switch-port locking technology for prevention of spoofing of MAC and the IP addresses. Also now about 150 virtual machines per XenServer host are supported. Also Open vSwitch to version 1.4.2 was updated.
• "Shared Nothing" Storage Migration - a possibility of hot migration of virtual machines between hosts and storages which are located on local disks of servers or storages, separate for hosts, i.e. not having the general storage. It becomes means of Storage XenMotion technology which works both in XenServer pools, and between them.
• Package converting of virtual machines from the VMware vSphere platform on XenServer - using the product XenServer Conversion Manager based on the separate virtual module (Virtual Appliance) it is possible to organize mass migration from infrastructure of VMware on XenServer now for those companies to which began to support the vSphere environment too expensive.
• Hot migration for VDI images - hot migration of storages of virtual machines in a VDI format of a virtual disk without idle time.
• XenServer Tools changes - now this packet for guest OS is delivered in a MSI format that allows to manage more flexibly its installation in guest OS.
• Emergency Network Reset is a possibility of rollback of a network configuration of hosts of XenServer to the last working configuration.
• VLAN Scalability improvements is the improved means on the VLAN setup in XenServer pools.
• About other insignificant innovations of XenServer 6.1 (like support of 4 GPU Pass-through) it is possible to esteem here.

Multiple vulnerabilities in Citrix XenServer

Experts of the research center Positive Research detected at the beginning of 2012 and helped to eliminate multiple vulnerabilities in Citrix XenServer. The reports submitted by the research center contain the description more than ten vulnerabilities of different risk levels.

One of vulnerabilities is, according to experts, critical and allows to receive in some cases dostupk to the password of the superuser of a system and full control over virtual infrastructure. Other vulnerabilities were found in the managing web interface of two Citrix XenServer applications: Web Self Service and vSwitch Controller.

Among the vulnerabilities detected in Citrix XenServer: cross-site accomplishment of scenarios (Stored XSS) in Citrix License Administration Console; cross-site substitution of a request in Citrix License Administration Console; failure in service in Citrix XenServer Workload Balancer; vulnerability at redirection of URL in Citrix XenServer Virtual Switch Controller; splitting of a HTTP request in Citrix XenServer Virtual Switch Controller; insufficient check of authorization in Citrix XenServer Virtual Switch Controller; cross-site substitution of a request in Citrix XenServer Virtual Switch Controller.

In turn, Web vSwitch Controller is the specialized managing virtual server (Virtual Appliance). The vulnerabilities detected in it are shown on XenServer 5.6, 5.6 SP 1/SP 2 and 6.0. For their elimination it is necessary to update vSwitch Controller to version 6.0.2.

2010

Citrix XenServer 5.6

The Citrix company at the very end of September, 2010 released a beta of the new version of a product for server virtualization of Citrix XenServer 5.6 Feature Pack 1 (the code name "Cowley"). Let's remind that the product Citrix XenServer allows to use functions of high availability of virtual machines (High Availability), to move them between servers without stopping (XenMotion), to balance load of a host servers and also to use StorageLink technology for integration into disk arrays. Besides, XenServer has also the equipment for work optimization a host servers with memory.

Now Citrix XenServer 5.6 FP1 had following features:

• Distributed Virtual Switching. This opportunity allows to use management tools the distributed network interaction a host servers and virtual machines (for example, cross-host private networks is an analog of PVLAN on dvSwitch in VMware vSphere). Also the Open vSwitch (OVS) device for XenServer hosts hosts and also the Controller component for management of several vSwitches is supported. Open vSwitch includes support of the big personnel of Jumbo Frames allowing to achieve the largest performance in networks of storage based on iSCSI.
•   VM Protection & Recovery is use of removal of mngnovenny pictures (snapshots) and export of virtual machines according to the schedule. The new version of XenServer includes the simple utility for a backup of virtual machines and their recovery (from the snapshot...).
• Web Self-Service. A self-service portal for users of virtual machines on the basis of the privileges determined by the administrator.
• Boot from SAN with multi-pathing support. A possibility of loading of hosts of XenServer via the Fibre Channel HBA adapter from SAN network.
• HA Restart Priority. A possibility of setup the politician of the mechanism of fault tolerance so that to place priorities on start of virtual machines refused a host server (for example, for auxiliary VM StorageLink Gateway VM or Distributed vSwitch Controller VM which should be started at first).
• Improved XenDesktop VDI scalability. Improvements under virtualization of desktop PCs (VDI) - increase in coefficient of consolidation of virtual machines at a host servers by means of use by the control domain component (Dom0) of several processors and other improvements.
• Enhanced XenCenter. The improved XenCenter management tools, including completely configured StorageLink, the reporting on use of VM and even a possibility of calculation of costs for virtual infrastructure (chargeback).
• Improved MPP RDAC multi-pathing is the reporting on the status of a way to configurations with nesokolky ways to DWH and also the reporting and a possibility of operation of notifications (health reporting and alerting).
•   Snapshot improvements. After removal of the snapshot - on storage system everything is accurately cleaned.
• Windows Oracle Linux Enhanced guest OS support - лучше работают: 7 SP1, Windows Server 2008 R2 SP1, RHEL 6.0 (RTM), CentOS 6.0 (RTM), Enterprise 6.0 (RTM), Debian Squeeze (32 and 64-bit) и SLES 11 SP1.
• Generic RHEL 5.x support. RHEL / CentOS / Oracle Enterprise Linux 5.0- 5.5 support with a generic "RHEL 5" template.
•   The Brocade HBA drivers - and also command prompt utilities are included in XenServer.
•   XenDesktop platform enhancements. Technology of local caching of images of virtual machines for economy of disk space in infrastructure of virtual PCs (VDI). It will be used in the next version of Citrix XenDesktop.

Notes

Links

• Anyone according to this link can download Citrix XenServer 5.6 FP1 Beta (the account MyCitrix is necessary).
• Virtualization of vSphere, Hyper-V, XenServer and Red Hat