Citrix's XenServer server virtualization technology doesn't have a huge market share. But that's not to say its insignificant: It has its followers--especially those looking to virtualize Linux workloads--and it has its place, often as a secondary platform for companies using VMware or, increasingly, Hyper-V.
When Citrix announces a major release, as it did last Friday with XenServer 6, it's definitely worth taking a look to see what's new. But first, let's take a look at how Citrix is selling the product, because the way a company does that can be very telling.
One key point Citrix would like you to know is that XenServer 6 is optimized for cloud computing and the "Cloud Era." In fact, the cloud computing message is threaded throughout Citrix's announcement, along with reminders that you can use XenServer 6 with Citrix's CloudStack cloud platform. Citrix acquired CloudStack when it bought Cloud.com in July. Because of that, the company decided to pull the Self-Service Manager feature, which was present in the beta version of XenServer from XenServer 6. Right now, CloudStack is great for public cloud service providers or Web 2.0 application companies, but it is not suitable for enterprises that want to run a private cloud in-house in their data center, according to Derek Slayton, Citrix's senior director of product marketing for XenServer. Apparently, the Cloud Era doesn't include private clouds, then. That's, ahem, surprising.
Avoiding cloud-talk, Slayton reckons the improvements for XenDesktop customers are the most exciting new features in XenServer 6. These include GPU Pass-Through, which enables a physical GPU to be assigned to a VM to provide high-end graphics, and enhancements to Citrix's HDX technology for "high definition" desktop virtualization.
Slayton also highlights another area of improvement. "Our work to simplify installation and management is pretty important. In the past we have tended to [shy] away from our "10 (minutes) to Xen" proposition, but in XenServer 6.0 we made it easier to use advanced features."
Slayton's other key point is that iXenServer is cheap--as in low cost, not low quality. The free version offers an astounding feature set, it has to be said, including the XenCenter Management Console and the vMotion-like XenMotion Live Migration. Other versions range from $1,000 to $5,000 per server, and are free of any "vTax" on virtual memory, Citrix promises.
So what else is new in XenServer 6?
Monster XenServer VMs
Everyone wants to compete with VMware's monster VMs, and in this release Citrix, based on the Xen 4.1 hypervisor, has doubled the number of virtual processors each VM can have to 16, and the maximum virtual memory per VM is now 128GB. The amount of physical memory supported on the XenServer physical hosts has also been beefed up to 1TB, while the hypervisor supports 64 logical CPUs (cores or hyperthreads). That's not quite up to VMware's monstrousness, but it is on par with Microsoft's.
Managed by Microsoft
The reality of XenServer is, as alluded to above, that it's often used as a secondary virtualization platform. If you happen to be a Hyper-V user, then you're probably using Microsoft's System Center management suite, and the good news is that you can now manage XenServer hosts and provision VMs with System Center Virtual Machine Manager (SCVMM) 2012. You can also monitor and troubleshoot them using System Center Operations Manager (SCOM) 2012. Slayton notes, however, that you'll still likely have to do some low-level stuff in the XenCenter Management Console.
No More Windows VMs
XenServer 6 supports remote data replication between storage arrays with fast recovery and failback capabilities using integrated Site Recovery. Previously, you had to use StorageLink Gateway Site Recovery in a VM with Windows to do this. Also, StorageLink Gateway technology, which required a VM with Windows, has been completely replaced with integrated Storage Link, which allows you to access existing storage array-based features, including data replication, de-duplication, snapshots and cloning right from XenServer 6. And let's not forget that the Windows virtual appliance for workload balancing has been replaced with a Linux-based virtual appliance, too.
New Virtual Switching
Open vSwitch is now the default networking stack in XenServer 6 (as well as other systems, including the CloudStack and OpenStack), providing formal support for Active-Backup NIC bonding. Citrix hopes it will increasingly be used as a foundation for cloud operations with support for distributed virtual networking and features, such as NetFlow, RSpan and security ACLs.
Other features include:
- Enhanced Guest OS Support: Support for 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). Experimental VM templates for CentOS 6.0 (32/64-bit), Ubuntu 10.10 (32/64-bit) and Solaris 10.
- Distributed Virtual Switch Improvements: A new fail-safe mode allows Cross-Server Private Networks, ACLs, QoS, RSPAN and NetFlow settings to continue to be applied to a running VM in the event of vSwitch Controller failure.
Paul Rubens is a journalist based in Marlow on Thames, England. He has been programming, tinkering and generally sitting in front of computer screens since his first encounter with a DEC PDP-11 in 1979.