Please be warned this comparison is biased toward VMware. For our un-biased comparison please check Microsoft Virtual Server 2005 R2 VS VMware Virtual Infrastructure 3 (un-biased).

	VMware	MS Virtual Server
Component Failure	NIC teaming, HBA multipathing	Relies on mgmt OS
OS/Application Outage	unplanned  VMware HA x-host VM Cluster planned  VMotion DRS Maint.mode	No Microsoft host pooling Complex Microsoft host clustering
Resource Shortage	VMware DRS	No Microsoft host pooling Irreversible hot add
Server Failure	VMware HA	Complex Microsoft host clustering
Files Deleted	VMware Consolidated Backup	No integrated backup tools
Storage Failure	VMware Consolidated Backup	No integrated backup tools
Interrupted Live Migration	VMFS distributed file locking	No distributed FS to prevent VM corruption
Cost Per VM	Low	Medium
64-bit Support	Production Support	Not Available
OS Support	32- & 64-bit, Windows, Linux,NetWare, Solaris guests	Limited Windows, Linux guests
Mgmt OS a single point of failure?	False	True
Hypervisor just an extension to a fat OS	False	True (Windows 2003)
Customer Support	Well established virtualization support	Adopted virtualization support and still building it.
Primary Customer usage	85% of VMware customers use server virtualization in production1	Primarily in test/dev environments
Requires Host OS	No - Bare-Metal Installation	Yes, Windows 2003 is required.
Performance	High	Low
Security	High	Host OS dependant (exposed to all Windows 2003 vulnerabilities)

Other Related Comparisons:

Windows Server 2008 Hyper-V R2 VS VMware vSphere

Xen Server Enterprise VS VMware Virtual Infrastructure 3

Microsoft Virtual Server 2005 R2 VS Xen Server Enterprise

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

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