Hyper-V is a key technology for Microsoft, and the company is throwing a lot of resources behind the development of what it hopes will become the preferred server virtualisation platform in enterprise datacentres. However, there are a few issues to bear in mind, some minor some less so.
Although the software can only be installed on servers with 64-bit processors, that's not too big a drawback: no self-respecting corporate will buy anything less, and 32-bit servers are as rare as hen's teeth anyway. Moreover, unlike Virtual Server 2005, Microsoft's hypervisor can host 64-bit as well as 32-bit guests, which means it can be used to run more demanding applications such as the latest 64-bit-only Exchange Server 2007.
Hyper-V also requires processors with either Intel VT or AMD-V hardware virtualisation extensions -- although, again, that's now very much a standard hardware feature.
On the plus side, Hyper-V is a lot more scalable than Virtual Server 2005, which is unlikely to be developed much further, according to Microsoft Server product manager Gareth Hall. This is understandable because Virtual Server 2005 is limited to 32-bit virtual machines with a single virtual processor per VM. By contrast, Hyper-V, even in its first release, can run either 32-bit or 64-bit guests with up to 4-way virtual SMP. Each Hyper-V guest can also have up to 64GB of memory, compared to just 3.6GB with Virtual Server 2005.
Indeed, the capabilities of Hyper-V come close to matching what's possible with VMware's ESX Server and catapult Microsoft straight into the top echelon of server virtualisation vendors. Of some concern, however, are the delays the company has encountered getting the product to market, together with compromises in terms of functionality that have been made to meet release dates.
Originally expected to be available along with the rest of Windows Server 2008, Hyper-V development has been dogged by problems. The official line is that it will now be a no-cost upgrade, available 'within 180 days of Windows Server 2008 being released to manufacturing'. The RTM date was 4 February so, according to that claim, Hyper-V ought to ship on or around 1 August. Although that's not too far away, it's still well behind both VMware and Xen.
Functionality has also been cut back since the original announcement, the most significant omission being the ability to migrate virtual machines from one host to another without shutting them down. This option is available both with VMware ESX Server and, more recently, XenServer Enterprise from Citrix. Microsoft is working on something similar that can take advantage of the enhanced clustering facilities in Windows Server 2008. However, it has yet to provide a firm date for when this will be introduced.
Fitting into the virtual landscape
As a late entrant to the hypervisor market, Microsoft faces a huge task if it expects to be able to oust VMware from its leading position. That doesn't mean it can't happen, of course. Hyper-V will benefit from being bundled as part of Windows Server 2008, and the market for server virtualisation is far from saturated. In fact, Microsoft reckons that less than 10 per cent of production servers are deployed this way. The company also has another trick up its sleeve, in the form of its VM management tools.
As with Virtual Server 2005, tools to manage individual Hyper-V deployments are included with the core software. But Microsoft has also recently added a Virtual Machine Manager (VMM) product to its System Center family, which can centrally manage virtual machines across multiple servers running both virtualisation platforms.
However, the ability to manage Hyper-V won't be added until shortly after the hypervisor is released. In the meantime, Virtual Machine Manager 2007 is limited to managing Virtual Server 2005, with VM interoperability between the two platforms allowing customers to start off with Virtual Server now and quickly upgrade when Hyper-V ships.
According to Microsoft, the next release of VMM will be able to manage VMWare virtual machines as well, with Citrix XenServer support to follow shortly thereafter. That's a wise move given general agreement that server virtualisation is unlikely to last very long as a separate application. To this end, Citrix has stated its intention to provide compete interoperability between its product and Hyper-V and the consensus is that hypervisors will, eventually, be embedded into server hardware. Indeed, Dell has already started down this route by offering XenServer, and soon Hyper-V Server, as a factory-fit option on its PowerEdge systems.
When that happens, customers will no longer be concerned about the technology involved or who it belongs to. Rather, the key differentiator, and the product that most organisations will buy, will be tools to manage virtual machines. That's already starting to happen and it's here, in the management tools rather than the underlying technology, that Microsoft looks to set to make its real mark on the server virtualisation landscape.
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That statement is not correct. It differs significantly from VMWare and other IO translation virtualisation products. It is however identicat to the Xen solution (except on Xen the primary partition runs Linux, not windows) and the API's are in fact compatible.
And Xen borrowed the idea from IBM (they even admit so on their website)