VMWare ESX / Microsoft Hyper-V Comparison

It’s time for the obligatory VMWare / Hyper-V comparison. This has been a popular topic in recent months, and now that I’ve had the chance to use both, I hope to provide a simple comparison and bring together some of the harder to find info regarding these popular virtualization solutions. Specifically I’ll be comparing Microsoft’s Hyper-V to VMWare’s ESX & ESXi (as well as comparing ESX to ESXi). This should be of interest to anyone who hasn’t yet begun to utilize virtualization, or who is considering a move from one platform to another.


Microsoft has been involved with virtualization for a number of years with their Virtual Server product, which is a host based virtualization solution (meaning it runs on top of a server OS). With the final release of Hyper-V in June of this year they entered into the hypervisor based market.

VMWare has a number of virtualization products. Their VMWare Server product is a host based solution somewhat like Virtual Server. In the hypervisor based market they have two similar products, ESX and ESXi. ESX is their traditional offering, released in 2001, which includes the hypervisor and built in management functionality (see the Management section below). ESXi is their small footprint, hypervisor-only edition which was released for free a few weeks ago. It doesn’t include the built in management utilities, and weighs in at only 32 MB in size. Unless otherwise mentioned below, “ESX” will refer to both ESX & ESXi.


Figure 1

Figure 1

While Hyper-V and ESX are both hypervisor based (“baremetal”) solutions, meaning they install directly on the hardware and require no lower level OS beneath them, the way they have been architected is very different. The ESX line installs a hypervisor on the hardware which acts as the intermediary between the hardware and any virtual machines running on the server (see Figure 1). Hardware device drivers are included in the hypervisor. This is called a direct driver model.

In similar fashion, Hyper-V installs on the bare metal, but all management functions and access to the hardware is controlled via a “root partition” that runs the Windows Server (or Server Core) 2008 OS. Server Core is the recommended OS. This root partition is actually a special virtual machine, through which hardware I/O requests from child partitions travel via the VMBus architecture (see Figure 2). This is called an indirect driver model. So basically before you enable the Hyper-V role, your server OS is of the typical architecture, after enabling the role, Hyper-V installs itself on top of the hardware, and places your original OS into this special virtual machine, the root partition.

Figure 2

Figure 2

There is also the concept, which I won’t get into, of “enlightened I/O” which are hypervisor aware OS’s (Vista, Server 2008, SUSE Linux), and typically perform better than “unenlightened” OS’s (NT, 2000 Server, other Linux). The Hyper-V hypervisor itself is only about 1 MB in size, but this stat alone is misleading because it requires the Server 2008 root partition. Even with only Server Core installed, the smallest footprint will be about 2.6 GB. A widespread misconception that I personally held until recently was that Microsoft also released a version of Hyper-V that was hypervisor only, and would not require the root partition or associated Server 2008 OS. It appears at this time that this is not the case, although it is apparently in the works.
UPDATE: Microsoft released the stand-alone version, “Hyper-V Server” on October 1, 2008.


A comparison of certain key features between platforms:

  • ESX supports both 32 & 64-bit hosts, Hyper-V requires a 64-bit host that supports hardware-assisted virtualization. All platforms support 32 or 64-bit guests.
  • Maximum Logical Host CPU’s: ESX = 32, Hyper-V = 16 (can do more, but not supported)
  • Maximum Supported Host Memory: ESX = 256 GB, Hyper-V = 2 TB (2008 Enterprise Ed.)
  • Maximum Memory per Guest OS (VM): ESX & Hyper-V = 64 GB
  • Maximum Supported Running VM’s: ESX = 128, Hyper-V = limited only by available resources
  • RAM Over-Commitment: Supported in ESX, not supported in Hyper-V. (This allows RAM allocated to VM’s to exceed actual available RAM in host).
  • NIC Teaming: Native support in ESX. Hyper-V only supports via 3rd party drivers.
  • Maximum # Virtual Switches: ESX = 248, Hyper-V = unlimited
  • ESXi Networking Shortcomings
  • All platforms support raw device mapping, 10 GB Ethernet, VLANs, Ethernet Jumbo Frames, 4-way SMP, iSCSI & FC SANs, and storage multipathing.
  • Performance metrics so far are hard to come by. Microsoft is not publishing performance numbers, currently only stating that they are “happy with the progress made on the performance side”.  VMWare meanwhile, has the opinion that “Hyper-V presents substantial limitations in all critical aspects of a hypervisor”. In my experience, both are powerful solutions, but it seems that Hyper-V is slightly less robust. The general opinion of others in the field seems to be the same.


Once you have a hypervisor installed, you need to be able to manage it in order to provision hardware, setup virtual machines, configure networking, etc. Each offering has different ways to perform these tasks.

Hyper-V management can be done in the root partition via the Hyper-V Manager MMC. This management console is similar looking to other Microsoft management utilities, and easy to navigate. In addition to using this tool to administer the virtual environment, hardware setup related tasks can be performed in the root partition using native OS tools. This tool can also be used remotely from another Server 2008 or Vista machine. The Hyper-V MMC is ideal for management of standalone virtual servers. For a more powerful, centralized management console, Microsoft will be releasing the System Center Virtual Machine Manager (SCVMM) 2008 product in September (at a cost of course). This enterprise ready product will also supposedly be able to manage VMWare environments.

The ESX line can be managed a number of ways. The Service Console, a Linux command line environment, can be used locally or remotely (via SSH) for administration. ESX also includes a web management interface. A final option, and the most feature complete, is the VMWare Infrastructure Client. This GUI utility allows administration of a standalone ESX server & guests, or of an entire farm of servers when combined with the Virtual Center Server option, which facilitates centralized virtual server management and other advanced features.

The ESXi line is only a bit more limited, as the trimmed down hypervisor doesn’t have the management features built in. There is no Service Console or web management in ESXi. It does, however, support a Remote Command Line Interface (RCLI), and supports administration via the VI Client (downloadable from the ESXi server).


A key point when evaluating a virtualization solution is the capability for high availability, redundancy, and mobility. VMWare is the clear leader in this category. ESX, when combined with the Virtual Center Server option, offers VMotion, Storage VMotion, High Availability (HA), and Distributed Resource Scheduling (DRS).

Hyper-V offers “Quick Migration”, which like VMotion enables the movement of a VM from one host server to another, but unlike VMotion requires downtime while the VM is suspended, moved, then restarted. VMotion does this on the fly with no downtime or loss of session data. Microsoft also offers a High Availability functionality, but that is reliant on MS clustering. This link summarizes all of the Hyper-V features.


The final but perhaps biggest consideration when deciding on a virtualization platform is cost. Both vendors have made changes recently to their pricing. The news related to Hyper-V touted that it would be priced at $28. While this is technically true, when considering the fact that it currently requires Server 2008, the actual price is closer to $999 (Standard Edition) or $3,999 (Enterprise). Using SCVMM will encur further cost.

The big news from VMWare was a recent announcement that ESXi would be available at no cost (previously $495). As mentioned, some of the management capabilities are limited in this version. The RCLI allows only for read-only access, meaning no configuration changes can be made, and there is no web admin interface. However, the ESXi platform can be administered with the powerful VI Client utility. To fully utilize advanced features (VMotion, HA, etc), ESXi needs to be licensed with VMWare’s Virtual Infrastructure platform. For anyone looking to get started with virtualization, this should be the obvious choice, as it offers a low cost (free!), powerful, easily upgradable path with an industry leader.

The ESX version is only available as part of the Virtual Infrastructure platform, which lists at $995 (Foundation version), $2,995 (Standard), or $5,750 (Enterprise). Another consideration is that the Virtual Center Server option is required in order to use features such as VMotion, HA, and DRS. This option starts at $6,000 and goes up from there.

Worth mentioning here, a bonus to virtualizing Windows Server ( 2003 or 2008 ) is that purchasing one Enterprise Edition license entitles you to run up to 4 virtual instances of the OS at no additional cost. One Datacenter Edition license entitles you to unlimited virtual instances. This is independent of the virtualization platform, so applies whether you use Hyper-V, VMWare, Xen, etc.


At this point in the race, VMWare does seem to be the clear leader. They have the majority market share, and making ESXi available for free only helps that position. I would wager that to most IT pros, they also have the more mature, reliable, and functional platform. However, Hyper-V is a first generation product which is quite capable for its age. History has shown that Microsoft is very adept at re-engineering ideas from other companies into their products and over a period of time becoming the dominant market leader (think Windows Server, Exchange, Internet Explorer, etc, etc). Factor in to that critical mistakes like this recent one from VMWare, and the fact that Hyper-V is included with most versions of Server 2008, and it isn’t difficult to foresee Microsoft taking the reins from VMWare at some point in the near future.

ESX / ESXi comparison
ESXi / Hyper-V comparison
Hyper-V FAQ


6 Responses

  1. […] http://blog.techscrawl.com/2008/08/14/vmware-esx-microsoft-hyper-v-comparison/ Published Friday, August 15, 2008 8:04 AM by rodtrent Filed under: Virtualization, Hyper-V, VMWare […]

  2. […] 31, 2008 by Bert Bouwhuis TechScrawl.com geeft in een compact overzicht de verschillen weer tussen Microsoft’s Hyper-V, VMware’s […]

  3. It seems VMWare is little bit better, but soon Windows Server 2008 R2 comes on the market, with improved Hyper-V. Race has begun, and that’s good news for system administrators :-)

  4. Hi,

    we are considering to buy a VMware Virtual Center.
    We have two servers running VMware Standard edition.
    Do you believe it will be worth it? Or do we have to
    upgrade our VMware licenses to Enterprise before upgrading
    virtual center to make it worth it. I had just read the
    following article
    VMware virtual center real value

  5. Well there are a few things to take into account. Judging by your comment, I’m assuming you mean you have the free VMWare Server edition which runs on top of an underlying OS? If you obtain one of the bare metal versions, ESX (costs $) or ESXi (free), you can migrate your VM’s to this platform. Virtual Center would then be worth considering to use advanced features like VMotion (live migration), High Availability, or DRS. It’s definitely worth it if you’ll use these features. As far as licensing, you’ll have to check with your vendor, but I believe you do need to upgrade to enterprise licensing. Hope that helps. This link lists the full Virtual Center features: http://www.vmware.com/products/vi/vc/features.html

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