Virtualisation suites compared

Virtualisation suites compared

Summary: Getting the foundation right for cloud means succeeding in virtualisation, but with multiple products available, which one is right for your business?


Citrix XenServer 6.0.201

Citrix has been working hard to improve its features and usability over previous incarnations of XenServer 5.6 in an attempt to overtake VMware. In some respects, it also eclipses Microsoft's Hyper-V.

XenCenter General and new VM
Citrix XenServer 6.0.201
(Credit: Enex TestLab)

It now tips the scales at 658MB (on the install CD). While it's a lot less than Server 2008 Hyper-V, it's still a good deal larger than VMware's vSphere, until you factor in that the CD also includes the hypervisor and XenCenter management utility. Once you start adding up the extra VMware bits and bobs, it is actually the leanest of the three.

It is also worth noting that XenServer takes a significantly different approach to its hypervisor, compared with Microsoft and VMware. The latter two predominantly use proprietary drivers and abstraction layers, whereas XenServer works with the hardware and existing drivers to simplify and speed up the hypervisor interaction with physical hardware.

For example, the XenServer control domain makes use of standard open-source device drivers, which should result in broader hardware support (although this is potentially a downside, due to a lack of vendor collaboration in driver hardening and/or patching). As another example, rather than using a proprietary file system, XenServer uses the native storage file system; VM snapshot requests are offloaded directly to the storage area network vendor's API.

Two separate physical boxes are required to run the XenCenter application and the XenServer host. The XenCenter machine requires a Microsoft Windows operating system — Windows 7, Windows XP, Windows Vista, Windows Server 2003, Windows Server 2008 or Windows Server 2008 R2 (all editions and versions).

Set-up is great. It's the easiest and most painless of the three hypervisors to install. The same CD is also used to load the XenCenter management console on a Windows-based PC.

To its credit, XenCenter is remarkably easy to use, and has a very clean interface; we consider it to be more user friendly than either Hyper-V or VMware. Creating, backing up and copying VMs is a doddle, as is adding other host servers to the cluster and generating performance statistics.

Host specifications are quite similar to Hyper-V — the limits guide notes that up to 130 logical CPUs are supported on a host machine, but this is dependent on the physical CPU type and 1TB of RAM. On the other hand, VM RAM is a little better than Hyper-V, but still lagging VMware at 128GB for Windows. A physical GPU can also be assigned to a VM, so the guest can leverage GPU instructions, which is very useful for delivering 3D graphical applications via virtual desktops.

There is a maximum of 16 nodes per cluster, and up to 800 VMs and dynamic memory allocation amongst VMs is supported.

Version 6 has improved guest OS support, including Ubuntu 10.04 (32/64-bit); updated support for Debian Squeeze 6.0 (64-bit), Oracle Enterprise Linux 6.0 (32/64-bit) and SLES 10 SP4 (32/64-bit); and experimental VM templates for CentOS 6.0 (32/64-bit), Ubuntu 10.10 (32/64-bit) and Solaris 10.

The improvements in virtual networking are in distributed virtual switching. A new fail-safe mode allows Cross-Server Private Networks, ACLs, quality of service (QoS), RSPAN and NetFlow settings to continue to be applied to a running VM in the event of vSwitch Controller failure.

A memory-over-commit feature is available, and is called Dynamic Memory Control (DMC), which is a "ballooning" operation, and is only available in the XenServer Advanced or higher editions. Ballooning is when the hypervisor is running low on memory, and it sets a target page into which the balloon driver will "inflate", creating artificial memory pressure within the VM, and causing the operating system to either pin memory pages or push them to the page file. However, it is not as mature as the memory-management of VMware, which uses three mechanisms for memory management: transparent page sharing (TPS), ballooning and compression.

Citrix has a powerful provisioning service that allows server workloads to be provisioned and re-provisioned in real time from a single shared disk image. This streamlines operations for administrators, as they can simply patch the master image. Dynamic workload streaming is particularly useful, because peak load periods and even migration between a testing and production environment can be catered for.

Fault tolerance is well supported, and a VM can be automatically restarted on another server, should a host fail. Or, if desired, a VM can be mirrored on another host for seamless failover. VM snapshots can be scheduled and archived, but high-availability features are only on XenServer Advanced Edition or higher.

For enterprise environments using XenDesktops with IntelliCache, or VMs protected via high-availability features, there is a limitation of 50 VMs or XenDesktop VMs per host.

XenServer is able to balance workloads, and it supports two optimisation modes. Performance Optimisation ensures that a minimum performance level is maintained, while Density Optimisation places the VMs on the minimum number of hosts.

The requirement for a separate licensing server, as with other Citrix products, is still true for XenServer. The "grace period" feature for disconnection of VMs and hosts from a licensing server (a non-receipt of a five-minute heartbeat message from the licence server) permits continued operation for up to 30 days without reconnection.

To ensure a seamless and simple migration across physical hosts, XenServer also supports virtual network switching.

Topics: Virtualization, Microsoft, Open Source, Oracle, VMware

Kick off your day with ZDNet's daily email newsletter. It's the freshest tech news and opinion, served hot. Get it.


Log in or register to join the discussion
  • Virtualisation suites compared

    I would have loved to see RHEV compared here as well! Red Hat Enterprise Virtualization.
    Nirmal Pathak
    • Side-by-Side Virtualization Feature Comparison

      @nirmalpathak I've put together a comparison of Citrix XenServer, Microsoft Hyper-V, VMware vSphere, Oracle VM and Red Hat for you here:

      (Full disclosure, I work for Ombud, an online platform to research enterprise technology. Ombud allows users to compare solutions feature-by-feature and then customize those comparisons according to their needs)
      • latest Server 2012 v vSphere 5.x v XenServer 6.x v Redhat KVM comparison

        Just posted this as response to a similar thread - one of the best for the above comparisons seems to be - at least it's always updated by the looks of it (not just a blog). Most of my guys use it - wish they would add more details on VDI and Cloud.

  • No comparison to Windows Server 2012

    Nice writeup, although don't you think it would have been appropriate to compare Server 2012? I guess it hasn't been officially released, so maybe we'll see another write-up in September.
    • Fanboy alert

      • The author included VirtualBox for no better apparent reason..

        ..than to give it some credit for being free and light.

        I would count this a lot closer to fanboyism than someone asking that one of the platforms being compared be the most current version.
  • Virtualisation suites compared

    i think you should watch these and and after that do a comparison (it is done there)
  • Why is VirtualBox in there?

    "it is not a direct competitor to the other three virtualisation implementations. "

    VirtualBox doesn't even belong in this comparison. As others have said, you dropped the ball by excluding RHEV (among probably others) that would have fit the bill much better.

    If you want to talk about VirtualBox, you should be including it in a comparison with VirtualPC, VMware Workstation (or VMware Player, if you strictly want to stick with "Free" offerings).

    You don't do Oracle or VirtualBox developers any kind of service comparing it to a Type-1 hypervisors, and you don't do your own readers (who might be looking for a useful comparison) any service, either.
    • Seriously

      Im quite confient if you where in person you could have said this more nicely. No since in being an "a s s" when its not necessary. Just make a nice recomendation.Read parson project above and see how humans interact.
      • You must be new here...

        "Im quite confient if you where in person you could have said this more nicely. "

        I'm quite confident I could also have been a much bigger jerk. Have a look at some of the more "popular" articles that get posted around ZDnet and I think you'll agree I was being quite tactful, relatively speaking.

        I chose to take the middle road and point out one or two reasons why it may be ill advised to include a desktop virtualization platform in a comparison with Type-1 Hypervisors, and why there may have been more relevant solutions that should have been included. It is possible that Steven and Thomas are experts when it comes to these technologies, but this type of oversight calls that expertise into doubt very, very quickly.

        If you prefer to take everything a blogger writes at face value with a pat on the back and a "nice write up", then so be it. I prefer bloggers be kept honest myself, and one of the best places to do that is in the comment section, disecting and challenging important assertions that those bloggers make.
        • Don't mind daffy

          He's always been a rude ass. He even beats me in that department. And that's a lot.

          • The one big difference..

   you tend to be rude without provocation.
    • I use VirtualBox and VMWare Player and I agree

      For Linux users VirtualBox is the best desktop virtualization suite. For a true hypevisor you have to go elsewhere.
      • Try out Workstation...

        VirtualBox does a good job of filling the gaps that the free VMware Player leaves, however give Workstation a comparison to VirtualBox (you can download a trial version for 30 days).

        I find the performance quite a bit better, and there are some features that just work better overall (snapshots, linked clones, which I know VirtualBox supports to a degree, but I find those much easier to manage in VMware, and I've also found it a lot more reliable).
  • Is this review for real?

    On August 5th 2012 you do you are review and use Windows 2008 R2 (Hyper V 2) and not the RTM version of Windows 2012 (Hyper V 3)??????????????

    I am no lover of Microsoft by far, but dam get a clue.

    Virtual box????????????? A layer 2 host product compared to the others?????
    • I agree.

      Sever 2012 with Hyper-v 3.0 did reach rtm last week, so it would have been logical to compare it instead of Hyper-v 2.0 certainly because the additions to it are major.

      Virtualbox does not compare to type 1 hypervisors, so is certainly out of place.