As one who has used both (and continues to), I would recommend Hyper-V, especially if you are primarily a Microsoft shop. We have migrated over 25 virtual machines from VMware to Hyper-V using SCVMM, and the migrations have been flawless. We needed more memory, as currently Hyper-V does not support memory compression/overcommit yet, but memory is cheap right now and Hyper-V has this feature comming soon.
VMWare also has live migration, but we have not seen a need for this. This feature is coming in the next release for Hyper-V
Hyper-V manager is fine if you have just have a couple of VM hosts, but SCVMM adds a number of useful functions, including libraries and combined view of VMware and Hyper-V hosts.
We will continue to use VMware as one of our servers is old and supports 32bit only, and we get some VMs from our clients. But all our new VMs are created using Hyper-V.
Broad support for Windows and non-Windows guest operating systems (10 Windows versions, 16 Linux versions, 2 Novell Netware versions and 2 Sun Solaris versions)
Uses the clustered/designed-for-virtualization VMFS (Virtual Machine File System)
Native support for Volume Snapshot Service (Shadow Copy)
Supports 64-bit and 32-bit versions of Windows Server, 32-bit and 64-bit Windows Vista and Windows XP Professional, SUSE Linux Enterprise Server 10 (32-bit and 64-bit) [source]
Uses the same management interfaces (command line, PowerShell, remote console) as other Server Core instances
Uses standard NTFS partitions, which can be a plus if you're in a Windows environment
Microsoft Hyper-V Server 2008 R2 (currently available as a Release Candidate) will feature Host Clustering and Live Migration (similar to VMware's vMotion technology) - Features not available with the standalone VMware ESXi product.
Ultimately, I think the decision comes down to your use case for virtualization:
If you're in a Windows environment and primarily interested in server consolidation, Hyper-V seems like a good fit
If you're in a Linux or mixed-OS environment, VMware ESXi will likely offer better support for your guest operating system
If you're interested in consolidation plus mature high availability, disaster recovery, etc., ESXi combined with VMware vSphere are currently your best options (with additional costs, of course)
People run a microsoft stack because the products integrate well with each other. Microsoft's virtualization isn't there yet, but there's no doubt they will be soon. Today, VMWare is better, but Microsoft is still good. If you have a mixed environment, I'd say to go with VMWare. If you're a Microsoft shop, then go with Microsoft.
Today, if you're a medium/large business with cash and a need for the bells & whistles, VMWare is the way to go. Bells & whistles = VMotion, Site Recovery Manager, power management, etc. If you're not a Windows shop, VMWare is the way to go.
If you're an SMB, HyperV is a no brainer -- just run your Linux in Xen or some other virtualization and your Windows in HyperV.
In 3-4 years when we get past the 1.0 release, Microsoft and VMWare are going to be neck and neck, with the usual Microsoft caveats.
I like the article from Massimo Re Ferre' A brief architecture overview of VMware ESX, XEN and MS Viridian at it20.ifo (It's a bit older, so refers to Hyper-V by its codename, Viridian, but it's still current as far as architecture goes.)
Regarding Kev's answer above ) on "How to Correctly Explain the Architectural Differences between Hyper-V and ESX: Greg Shields is a knowledgeable guy but describing the details of hypervisor architecture in a simple way can get tricky. Ken Cline lays out a few corrections in his blog post, Reaction to: “How to Correctly Explain the Architectural Differences Between Hyper-V and ESX” at kensvirtualreality.wordpress.com (Full disclaimer: I work for VMware and Ken recently joined VMware.)
Fortunately, the precise details of the architecture don't matter much in day-to-day sysadmin life.
(I'm new, so I can't post links, so feel free to add them to this answer.)
Great points here! I'm not going to give my opinion since I work with Microsoft and it would be biased, but I'd definitely like you guys to talk to us on Twitter if you're there!
We're @MSSpringboard, the official Windows 7 IT Pro feed and @CIOsConnect, where we talk more about the enterprise site and lots of virtualization conversation.
I'm always looking to hear opinions and especially from people with experience so I'd be glad to hear from you guys there.
This is probably one of the best articles I've read so far comparing Hyper-V and VMWare ESX:
Update
The link above no longer works so here's WayBackMachine's last known snapshot:
Wayne (see comments below) also suggested a couple of alternatives.
The first is a response to the original and now defunct article:
The second article has unfortunately had the video removed from YouTube.
As one who has used both (and continues to), I would recommend Hyper-V, especially if you are primarily a Microsoft shop. We have migrated over 25 virtual machines from VMware to Hyper-V using SCVMM, and the migrations have been flawless. We needed more memory, as currently Hyper-V does not support memory compression/overcommit yet, but memory is cheap right now and Hyper-V has this feature comming soon.
VMWare also has live migration, but we have not seen a need for this. This feature is coming in the next release for Hyper-V
Hyper-V manager is fine if you have just have a couple of VM hosts, but SCVMM adds a number of useful functions, including libraries and combined view of VMware and Hyper-V hosts.
We will continue to use VMware as one of our servers is old and supports 32bit only, and we get some VMs from our clients. But all our new VMs are created using Hyper-V.
We have also been using SCVMM, and have created libraries of our common configurations. Provisioning a new VM, including naming and joining to the domain is all automated. We are looking to further automate using Powershell, see: http://msevents.microsoft.com/CUI/WebCastEventDetails.aspx?EventID=1032409528&EventCategory=4&culture=en-US&CountryCode=US
Overall, features, ease of use, and cost lead us to move to Hyper-V from VMware.
The most direct comparison is VMware ESXi vs Microsoft Hyper-V Server 2008:
VMware ESXi
Microsoft Hyper-V
Ultimately, I think the decision comes down to your use case for virtualization:
VMWare - pros=maturity, functionality & speed, cons=cost
HyperV is the opposite.
People run a microsoft stack because the products integrate well with each other. Microsoft's virtualization isn't there yet, but there's no doubt they will be soon. Today, VMWare is better, but Microsoft is still good. If you have a mixed environment, I'd say to go with VMWare. If you're a Microsoft shop, then go with Microsoft.
Today, if you're a medium/large business with cash and a need for the bells & whistles, VMWare is the way to go. Bells & whistles = VMotion, Site Recovery Manager, power management, etc. If you're not a Windows shop, VMWare is the way to go.
If you're an SMB, HyperV is a no brainer -- just run your Linux in Xen or some other virtualization and your Windows in HyperV.
In 3-4 years when we get past the 1.0 release, Microsoft and VMWare are going to be neck and neck, with the usual Microsoft caveats.
The only mature one is VMware so far.
I like the article from Massimo Re Ferre' A brief architecture overview of VMware ESX, XEN and MS Viridian at it20.ifo (It's a bit older, so refers to Hyper-V by its codename, Viridian, but it's still current as far as architecture goes.)
Regarding Kev's answer above ) on "How to Correctly Explain the Architectural Differences between Hyper-V and ESX: Greg Shields is a knowledgeable guy but describing the details of hypervisor architecture in a simple way can get tricky. Ken Cline lays out a few corrections in his blog post, Reaction to: “How to Correctly Explain the Architectural Differences Between Hyper-V and ESX” at kensvirtualreality.wordpress.com (Full disclaimer: I work for VMware and Ken recently joined VMware.)
Fortunately, the precise details of the architecture don't matter much in day-to-day sysadmin life.
(I'm new, so I can't post links, so feel free to add them to this answer.)
Great points here! I'm not going to give my opinion since I work with Microsoft and it would be biased, but I'd definitely like you guys to talk to us on Twitter if you're there!
We're @MSSpringboard, the official Windows 7 IT Pro feed and @CIOsConnect, where we talk more about the enterprise site and lots of virtualization conversation.
I'm always looking to hear opinions and especially from people with experience so I'd be glad to hear from you guys there.
Oh, and I really like Hyper-V :)
Cheers,
Alex Microsoft Windows Client Team