Server Virtualization Buying Guide -- Xen Server

by Paul Rubens

Citrix XenServer may not be the most advanced or robust server virtualization platform, but organizations with simple virtualization requirements or those looking for a supplementary virtualization solution will be more than satisfied with it.

Citrix has a very simple proposition with its XenServer virtualization platform: It may not be the most advanced in terms of features, but it has many of the features that you need, it works well and it costs less than most alternatives.

And that's an attractive proposition. XenServer is primarily designed to attract businesses with less sophisticated virtualization requirements as well as those that already use vSphere or Hyper-V for heavy duty virtualization but need something less-expensive for simpler virtualization tasks.

"By and large, the market is adopting a multi-hypervisor approach, choosing the best hypervisor for each job. Companies are adopting XenServer for departmental use and for less mission-critical applications," said Derek Slayton, Citrix's senior director of product marketing for XenServer. "We can deliver the features they need at 20 percent to 30 percent of the cost of VMware."

The XenServer platform is built on top of the open source Xen hypervisor, and it comes in four editions: Free, Advanced, Enterprise and Platinum. Pricing is as simple as can be: The Free version is free, while the others are charged on a per-host server basis.

The Free version is actually surprisingly comprehensive, offering:

  • A virtualization hypervisor
  • XenCenter management console for virtualization management
  • Virtual machine conversion tools
  • VM disk snapshot and revert
  • XenMotion Live Migration

Slayton said the target market for the Free edition is companies with one to 10 servers, although some organizations use it with hundreds of hosts. "The Free edition is production-ready, not limited, and capable of being run at large scale," said Slayton. "It's very good server virtualization at no cost."

The Advanced edition is both the next version up and the most recent addition to Citrix's XenServer product line-up. For $1,000 per server the Advanced edition adds 24 x 7 support and a handful of extra features including:

  • Automated VM protection and recovery
  • Distributed virtual switching
  • High availability
  • Memory optimization
  • Performance alerting and reporting

This balance of features and cost is beginning to find some customer uptake, "eating around the edges of (VMware) ESXi production environments," according to Slayton.

Citrix's most popular XenServer edition is the Enterprise edition, which builds on the Advanced edition with the addition of:

  • Dynamic workload balancing
  • Host power management
  • IntelliCache storage caching
  • Live memory snapshot and revert
  • Provisioning Services (virtual)
  • Role-based administration
  • StorageLink storage features
  • Web management console with delegated administration

This provides all the features that most companies require for fairly large-scale virtualization with multiple servers, multiple applications, dynamic power management and a good level of automation, Slayton believes."With this you can run a lights-out data center," he said.

What's noticeable about this edition -- and indeed the Platinum edition, which we will come to shortly -- is the lack of an equivalent to VMware's Storage vMotion or Microsoft's Storage Live Migration (slated for release in Hyper-V 3). Slayton said Citrix currently has no intention of adding a similar feature because in the company's view there is no need. "Storage Live Migration is an innovation from VMware that they charge for and many customers don't use," explained Slayton. "We focus on features at the midpoint of the market at a better price than VMware offers them. That's why we see a high use of XenServer around existing VMware deployments."

The high-end version of XenServer is the Platinum edition, which brings two heavy-duty features in to the mix:

  • Provisioning services
  • Site recovery

Essentially, the Platinum edition is all about failover capabilities, offering full site-to-site recovery for mission-critical installations. "VMware Site Recovery costs about $3,000 to $4,000 per core," said Slayton. "Our solution is much cheaper -- we offer simple, powerful cost-effective server virtualization with site recovery for $5,000 per server."

When it comes to management, XenCenter is included in all the XenServer editions, but it's worth pointing out that it is not a multi-hypervisor management system. That could be an issue given that, as Slayton repeatedly points out, XenServer is often used as part of a multi-hypervisor server virtualization solution. The good news is that in XenServer 6, released September 30, a XenServer fabric can actually be managed by Microsoft's System Center Virtual Machine Manager and Operations Manager along with Hyper-V VMs (and VMware VMs too.) "We work closely with Microsoft," said Slayton, "and since their virtualization system is built in to their OS, customers are bound to use it. But sometimes they will want to run stuff on our hypervisor -- especially Linux workloads or Xen Desktop -- and this integration with System Center allows customers to use the right hypervisor for the right job."

As far as the public cloud is concerned, Slayton said he believes Citrix has that covered with CloudStack, the infrastructure as a service (IaaS) platform Citrix owns as a result of the acquisition of Cloud.com in July 2011. CloudStack supports VMware's vSphere and Red Hat's open source KVM hypervisor as well as XenServer. Along with Cloud Portal -- for metering, billing and self-service provision -- this provides a cloud solution for telcos, service providers and web application providers. However, as far as implementing a full private cloud solution with a self-service portal for users to grab the application services they need from a catalogue, the cloud.com technology is not quite there yet.

In the meantime,there is a web self-service utility that provides access to virtual machine environments in XenServer 6, Slayton confirmed; however, a more sophisticated and robust self-service portal was pulled from the release. That's because in the near to midterm CloudStack will provide that functionality, but it's not available to enterprises yet. "When we acquired Cloud.com, we had to make this hard decision not to put our old technology in the hands of our customers because it is a dead-end and the technology will be changing."

Pricing (per Server)

XenServer Free edition: Free

XenServer Advanced edition: $1,000

XenServer Enterprise edition: $2,500

XenServer Platinum edition: $5,000

CloudStack: $1,500 (subscription)

This article was originally published on Wednesday Dec 21st 2011
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