There is no black-and-white answer to the question of which server virtualization platform to choose. If someone tells you there is, he's probably wearing a salesman's hat. I don't wear that hat, so I'll try to help you make an informed decision with some platform comparisons.
At the time of this writing, there are five server virtualization solutions: VMware ESX Server 2.5.3, VMware Server,
Microsoft Virtual Server 2005 R2, Xen 3.0 and XenEnterprise. Let's start with a brief introduction to these products:
- VMware ESX Server 2.5.3 is the current industry leader when it comes to server virtualization. It has a
steep entry cost, but it is well supported by the vendor and third
parties, and it works with fantastic results straight out of the box.
- VMware Server is a free, stripped-down version of ESX, with the primary difference being that it requires an
existing host operating system (OS) to run. For a complete list of differences between
VMware ESX Server 2.5.3 and VMware Server, see http://www.vmware.com/products/server_comp.html.
- Microsoft Virtual Server 2005 R2 is geared towards Windows server virtualization, but Microsoft recently
announced support for Linux guests as well. Although it is many times
overlooked, do not ignore Microsoft when it believes in a technology.
- Xen 3.0 is the current version of the Xen virtual machine monitor (VMM). It is open source and is rapidly
being adopted by the heavyweights in the industry, such as IBM, HP,
Intel, Red Hat, AMD and Novell, as the choice technology for server
virtualization.
- XenEnterprise springs forth from the company XenSource, founded by the creators of Xen. XenEnterprise is a
packaged version of the Xen software and will provide a similar
vertical virtualization solution to VMware's ESX Server.
Criteria
In this four-part tip, I will first describe the criteria for evaluation and evaluate the...
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options in terms of administrative features. In part two, I will discuss
technical specifications and support. Part three will go over management and high availability. Finally, part four will compare the options in terms of extra features and give a summary of the evaluation.
(These criteria borrow heavily from the VMware server
product comparison chart.)
Administrative
Management
- Cost
- Open source
- Service Level Agreement (SLA) enforcement (service level guarantees)
- Web-based server management
- Remote VM console
- Scripting and API support
- Template support
Technical specifications
High availability
- Host / control OS
- CPU support
- System RAM support
- Hardware compatibility
- Virtual SMP support
- VMs per CPU core
- Virtualization Mode
- NIC teaming
- VM clustering
- Storage area network (SAN) connectivity
- Host VM migration capability
Support
Additional features
- Vendor support
- Community support
- Third-party support (consulting and development)
- Available physical-to-virtual (P2V) solution
- Integrated monitoring solution
- Integrated backup solution
Processor
All the comparisons assume that VMM is running on an Intel
processor that supports Intel Virtualization Technology (VT-i, VT-x).
Host / control OSs
When a host or control OS is required, the following will be used:
VMM
Host OS
VMware Server
- Windows Server 2003 R2, Datacenter Edition x64
- Red Hat Enterprise Linux Version 4
Microsoft Virtual Server 2005 R2
- Windows Server 2003 R2, Datacenter Edition x64
Xen 3.0
- Red Hat Enterprise Linux Version 4
XenEnterprise
- Red Hat Enterprise Linux Version 4
Sources
My information for the following comparisons is derived from the
material I found online about the products, by reading white papers
and other related documents, talking with VMware engineer Michael
Wilson, and a phone conversation with Simon Crosby, CTO of XenSource,
on 2006/5/10.
Administrative
Read on to learn how the major options compare in terms of administrative features.
Cost
I
will not be addressing Total Cost of Ownership (TCO), only the
monetary cost of the product itself.
Standard Cost
With Educational Discount
VMware ESX Server 2.5.3 Virtual Infrastructure Node
(VIN)
(includes SMP and VMotion agents)
$5,000
$2,835.00
Grepped from known purchase order
VMware Server
Free
-
Microsoft Virtual Server 2005 R2
Free
-
Xen 3.0
Free
-
XenEnterprise
Priced for
the volume market
Per conversation with Simon Crosby, XenSource CTO
-
With three of the products being given away, ESX and XenEnterprise
better offer some key features to be worth their price points.
Winner(s): VMware Server,
Microsoft Virtual Server 2005 R2, Xen 3.0
Loser(s): VMware ESX Server
2.5.3, XenEnterprise
Open source
This section evaluates whether or not the VMM is open source software.
Open source
VMware ESX Server 2.5.3
No
VMware Server
No
Microsoft Virtual Server 2005 R2
No
Xen 3.0
Yes
XenEnterprise
Yes
Xen 3.0 and XenEnterprise are the only
VMMs in this comparison that are open source, a huge benefit to those
who wish to better understand and modify VMMs. This also means that
investors in virtualization do not have to worry about a vendor going
out of business and taking their source code with them. (There are ways to obtain source code from VMware, but it is still not open source.)
I do not necessarily believe that software immediately gets a black
mark for not being open source, so the closed-source solutions do not
lose points, but Xen does gain them.
Winner(s): Xen 3.0,
XenEnterprise
Loser(s): --
Service level guarantees
Service level guarantees ensure defined allocations of VM
resources such as CPU, memory, disk and network.
Service level guarantees
VMware ESX Server 2.5.3
Yes
VMware Server
No
Microsoft Virtual Server 2005 R2
No evidence
to support or deny
Xen 3.0
Yes
XenEnterprise
Yes
All the solutions offer service level guarantees with the
exception of VMware Server and Microsoft Virtual Server 2005 R2.
While they may not seem like a big deal, service level guarantees
help you enforce Service Level Agreements (SLA). Service level
guarantees are a crucial feature of any virtualization solution.
Winner(s): VMware
ESX Server 2.5.3, Xen 3.0,
XenEnterprise
Loser(s): VMware Server,
Microsoft Virtual Server 2005 R2
Click here to read part two, which discusses technical specifications and support.
Andrew Kutz has been professionally involved in the technology sector for 11 years. For the last six of them he has worked with the latest technologies while employed by the University of Texas at Austin. He started his own consulting firm and development house, . He is also a founding member of the Austin VMware Users' Group (VMUG). His current pet development project is Sudo for Windows.
