Please be warned this comparison is biased toward Xen. For our un-biased comparison please click Xen Enterprise 4 VS VMware Virtual Infrastructure 3 (Un-Biased).

	VMware	Xen
Price	$1000 - $5750	Free - $2499
Live Migration	VMotion	XenMotion
Required Host OS (if any)	Infra v3:Bare-Metal	Xen: Bare-Metal
Performance	Medium Instructions are emulated	Higher when the OS support Paravirtualization as the instruction is directly passed to the hardware.
Support Sata Controllers	Limited Sata Controllers	Wide array of Sata Controllers
Drivers Support	Limited Drivers Certification	Many Linux Drivers Certifications.
Max # of CPUs per Virtual Machine Max Memory per Virtual Machine Max Memory per Host	4 Processors 16GB 64GB	8 Processors 32GB 128GB
64-bit Support	Production Support	Production Support
Open Source	No it is closed source no chance to modify the code	Yes, fully open source
Provide Free Version	False	True (Express is free)
Hot Add CPUs to Linux Virtual Machines	False	True
Making use of Future windows enlightenments	No, Not yet	Yes, and are waiting for it to give a blazing speed to windows Guest OS.
Primary Customer usage	85% of VMware customers use server virtualization in production1	Primarily in test/dev environments

Other Related Comparisons:

Windows Server 2008 R2 Hyper-V VS VMware ESX 4.0

Microsoft Virtual Server 2005 R2 VS Citrix Xen Enterprise

Microsoft Virtual Server 2005 R2 VS VMware Virtual Infrastructure 3

Microsoft Windows Hyper-V (WSV) VS VMware Virtual Infrastructure 3.5

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