A recent SearchServerVirtualization article is rather interesting, reporting a survey made among readers reveals 40% VMware customers also uses Microsoft Virtual Server 2005. No reasons are provided to explain this overlapping but in my experience virtualization customers implements both technologies to understand which one is easier to manager, or better integrates in their own infrastructure, or has better performances. More rarely it just depends on political reasons, to avoid vendor lock-ins or to blindly follow advices from preferred system integrator. The article is also interesting because it implictly compares Microsoft Virtual Server with VMware ESX Server, and reports customer prefer the former when:

• are unfamiliar with Linux (needed to do basic administration under ESX)
• need a faster and cheaper starting solution (since Virtual Server is free of charge)

This comparison is pretty odd since VMware releases Server (formerly GSX Server) which is as free as Virtual Server 2005, and it's available both for Linux and Windows, so companies using only Microsoft technologies still can spend their knowledge without wasting time in new training. The inappropriate similarity between VMware ESX Server and Microsoft Virtual Server 2005 is unfortunately pretty common and depends on several factors:

• VMware poor marketing message, snubbing GSX Server since ever and pushing ESX Server as the only reliable enough product to be used in production
• Microsoft misleading marketing message, pushing Virtual Server as really able to compete with ESX Server (which, as said so many times, is not the case)
• Hundreds of consultants and tents of journalists, poorly skilled on one or another product, spreading confusing messages to already confused customers