During evaluations of server virtualization platforms, focusing on product features alone isn't such a good idea. A product is only as great as the stuff that comes with it. In part one of this four-part series, I discussed the criteria
for our comparisons and looked at administrative features. Now, I'll continue the platform comparisons with an overview of technical specifications and support.
Technical Specifications
Let's compare the virtualization options -- VMware ESX Server 2.5.3, VMware Server, Microsoft Virtual Server 2005, Xen 3.0 and XenEnterprise -- in terms of
seven technical support criteria.
Host / Control OS
Some VMMs require a separate host OS or control OS.
Host / Control OS
VMware ESX Server 2.5.3
-
VMware Server
Windows Server 2003, Linux
Microsoft Virtual Server 2005 R2
Windows XP
SP2 (non-production use), Windows Server 2003
Xen 3.0
Linux, FreeBSD
XenEnterprise
-
VMware ESX 2.5.3 and XenEnterprise get a point each for providing
a seamless installation without needing to separately configure a
host or control OS. VMware Server, Microsoft Virtual Server 2005 R2
and Xen 3.0 require configuring a host OS or control OS separate from
the VMM configuration, and for this reason they lose a point.
Winner(s): VMware ESX
2.5.3, XenEnterprise
Loser(s): VMware Server,
Microsoft Virtual Server 2005 R2, Xen 3.0
CPU support
Here, we look at the number of CPUs supported by the VMM.
CPU support
VMware ESX Server 2.5.3
16
VMware Server
16
Microsoft Virtual Server 2005 R2
Physical
processors supported by host OS
(up to 64 with Windows Server 2003 R2 Datacenter x64 Edition)
Xen 3.0
32
XenEnterprise
32
Wow, VMware really comes out behind here. Microsoft for the win.
Winner(s): Microsoft
Virtual Server 2005 R2
Loser(s): VMware ESX Server
2.5.3, VMware Server
System RAM support
Now we'll look at the amount of RAM supported by the VMM.
System RAM support
VMware ESX ...
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Server 2.5.3
64 GB
VMware Server
64 GB
(limited by host OS)
Microsoft Virtual Server 2005 R2
64 GB
Xen 3.0
16 GB
XenEnterprise
16 GB
Xen 3.0 and XenEnterprise support Intel's Physical Address
Extension (PAE) that allows up to 64GB of RAM, but currently Xen only
supports 16GB of RAM. Until Xen supports the allowed 64GB, the other
VMM solutions can tout four times the amount of supported system RAM.
Winner(s): VMware ESX
Server 2.5.3, VMware Server, Microsoft Virtual Server 2005 R2
Loser(s): Xen 3.0,
XenEnterprise
Hardware compatibility
This next comparison looks at the level and scope of the hardware on which the VMM will function.
Hardware compatibility
VMware ESX Server 2.5.3
Requires drivers from VMware
VMware Server
Compatibility
inherited from host OS
Microsoft Virtual Server 2005 R2
Broad
compatibility
Xen 3.0
Broad
compatibility
XenEnterprise
Broad
compatibility
The usual heavyweight falls short here. ESX relies on
vendor-supplied drivers to support hardware, while the rest of the
VMMs support an extremely broad range of hardware devices.
Winner(s): VMware Server,
Microsoft Virtual Server 2005 R2, Xen 3.0, XenEnterprise
Loser(s): VMware ESX Server
2.5.3
Virtual SMP support
This section takes a look at whether or not the VMM supports presenting the VMs two or more
processors.
Virtual SMP support
VMware ESX Server 2.5.3
Yes, up to two
VMware Server
Yes, up to two
Microsoft Virtual Server 2005 R2
No
Xen 3.0
Yes, up to 32
XenEnterprise
Yes, up to
32
There are no winners and losers, but if there were, Microsoft
Virtual Server 2005 R2 would have a huge fluorescent green "L"
painted on its forehead. Xen 3.0 and XenEnterprise are the clear
winners with support for presenting VMs with up to 32 processors.
Winner(s): Xen 3.0,
XenEnterprise
Loser(s): Microsoft Virtual
Server 2005 R2
VMs per CPU core
How many VMs does each need to run per CPU core?
VMs per CPU core
VMware ESX Server 2.5.3
4-8
VMware Server
2-4
Microsoft Virtual Server 2005 R2
Microsoft is
not clear on this
Xen 3.0
No evidence
found
XenEnterprise
No evidence
found
VMware is the only vendor that comes out and specifies the number
of VMs that can run per CPU core. They win for their recommendation,
but it is just that, a recommendation. The number of VMs per CPU core
does depend heavily on overall usage of the host server. For that
reason, Microsoft and Xen do not lose points for not giving their own
suggestion.
Winner(s): VMware
ESX Server 2.5.3, VMware Server
Loser(s): --
Virtualization mode
What's the type of virtualization being implemented with each option?
Virtualization Type
VMware ESX Server 2.5.3
Hardware virtualization (HVM)
VMware Server
Hardware virtualization (HVM)
Microsoft Virtual Server 2005 R2
Hardware virtualization (HVM)
Xen 3.0
Paravirtualization
(PVM), Hardware virtualization (HVM)
XenEnterprise
Paravirtualization
(PVM), Hardware virtualization (HVM)
Xen has led the paravirtualization revolution, and the speed
benefits are tremendous. With Intel VT, Xen can also use HVM to
virtualize Windows guests as well. We'll see what the future holds
for the rest of the bunch, but for now Xen takes the cake.
Winner(s): Xen
3.0, XenEnterprise
Loser(s): VMware ESX
Server 2.5.3, VMware Server, Microsoft Virtual Server 2005 R2
Support
Let's now turn our attention to the support available for each major virtualization option.
Vendor support
Does each vendor offer an official support channel for
the product?
Vendor support
VMware ESX Server 2.5.3
Yes
VMware Server
Yes
Microsoft Virtual Server 2005 R2
Sort of
Xen 3.0
Yes
XenEnterprise
Yes
VMware ESX Server 2.5.3 and VMware Server win this round, simply
by virtue of having a more established presence and better being able
to provide product support. The Xen products do not lose points
because there is vendor support, but they do not win points either
because they have not been in the game long enough to get a a sense
of the quality of their support.
Microsoft seems to be following in
the trend of Terminal Services when it comes to offering official
support for their Virtual Server platform. Microsoft Premier Support
Services (PSS) rolls Terminal Services into their Directory Support
team. I have personally been involved in problem resolutions that
have taken longer than a month and a half to fix because Microsoft
cannot get a hold of anyone that knows Terminal Services well enough
to help me figure out the problem. I fear that their Virtual Server
platform could suffer the same fate if more attention is not paid to
it.
Winner(s): VMware ESX
Server 2.5.3, VMware Server
Loser(s): Microsoft Virtual
Server 2005 R2
Community support
Now we'll look at whether or not there is community/grass-roots support for the
product.
Community support
VMware ESX Server 2.5.3
Yes
VMware Server
Yes
Microsoft Virtual Server 2005 R2
Yes
Xen 3.0
Yes
XenEnterprise
Yes
While all of the VMMs do enjoy community support, ESX and Xen win
because of the sheer number of their partners they have and the
zealous grass-roots followings they command. Microsoft's Virtual
Server products have traditionally not had the type of overwhelming
community support that VMware has enjoyed, or Xen is starting to
enjoy.
Winner(s): VMware ESX
Server 2.5.3, Xen 3.0, XenEnterprise
Loser(s): Microsoft Virtual
Server 2005 R2
Third-party support (consulting and development)
This table examines whether or not there is third-party consultation support as well
as third-party development for the product.
Third-party support (consulting and development)
VMware ESX Server 2.5.3
Yes
VMware Server
Yes
Microsoft Virtual Server 2005 R2
No
Xen 3.0
Yes
XenEnterprise
Yes
VMware ESX Server 2.5.3 and Xen win yet again. This is due in
large part to their loyal followings.
Winner(s): VMware ESX
Server 2.5.3, Xen 3.0, XenEnterprise
Loser(s): Microsoft Virtual
Server 2005 R2
This concludes our look at the technical specifications and support offered by each vendor. Read part three to find out about management and high availability.
