To virtualise is - well, virtuous - and also all the rage. Market leader VMWare has just brought out a new version of its long-established GSX Server 3 aimed at server consolidation. Microsoft is still a few months away from releasing Virtual Server 2004 (VS), now in beta, and is among the fruits of Microsoft's acquisition of Connectix' technology just over a year ago. It will join Microsoft’s now established Virtual PC package for workstations. And storage vendors can't stop talking about it.
Virtualisation software sits on top of a base OS, such as Windows Server 2003. Instead of running applications directly on top of the single OS, it adds a layer that virtualises the hardware. You can then load another OS and set of applications, each set running securely in its own container or virtual machine (VM). VM software can create as many virtual machines as you need, up to the limits of the hardware. Of course, this idea isn’t new - IBM mainframes used it back in the 1960s.
What is new is the growth of multi-processor setups, especially in the Intel server market. Here, with Intel planning multiple CPUs on a single chip, the scope for virtualisation at a reasonable hardware cost is bound to increase.
Benefits
So what problems does virtualisation fix - in theory at least? From a workstation point of view, developers find virtual machines a boon. It allows them to build an application or application subsystem in isolation from the test virtual machine (VM), test the software without affecting the development environment and switch back again. Any enterprise with its own development team, however small, can save on both hardware and programming time.
But it’s in the server area that virtualisation is making its biggest impact. Among the biggest problems for managers of server farms is heat. Today's CPUs dissipate up to 100W of power. Add heat-generating ancillary devices, from hard disks, graphics cards and SCSI subsystems, to gigabit network adapters and other I/O devices, and excess heat becomes a major headache.
In an office environment, you could easily add extra cooling to PC clients to dissipate heat, the power draw and heat dissipation not being perceived as major problems.
The server room's another affair. With floor space at a premium, enterprise servers are typically densely packed in racks and surrounded by other equipment, with the aircon roaring away at full blast. Yet there are always more demands, whether email serving and filtering, new applications, or more demand from the Web. Each demands a new server, each of which needs space, management and cooling. Common sense if not intervention by the CIO means that, at some point, despite the need for more functionality, the burgeoning of additional servers has to be curtailed if costs are not to spiral.
At this point, application virtualisation starts to make sense. Not only can it save on hardware costs, it means you’re using existing hardware more effectively. Rare are the CPUs that always run fully utilised, so why throw away that spare processing power? Microsoft punts it as a way for IT managers to mix both older and newer systems and applications.
Risks
The big question is of course reliability. Failure of an overheated CPU, or a buggy device driver, will result in the stalling of several applications rather than just the one you’d lose if you were still running one isolated application per box. Virtualisation itself can also generate problems that can be tricky to resolve.
On the other hand, if a virtualised OS crashes, it can do so without affecting other processes running on the same hardware. Virtualisation could even result in greater reliability, given that there are fewer hardware components to fail.
Hidden issues
However, there may be hidden gotchas. For example, software pricing is predicated as a rule on a single application machine. Add CPUs and the price goes up, but not in direct proportion to their number. However, you need to check how software vendor price their products when running on one of 12 VMs on the single piece of hardware. Does that result in a 12-way price point? You may have some negotiating to do with your software vendor.
Two vendors
Exact comparisons between VMware GSX Server 3 and Microsoft’s VS are hard to make, since the Microsoft product is still in beta; it’s not finished. What’s more, details of its feature set are also hard to come by. That said, the Microsoft product includes support for SCS, two-node clustering, and a host of support for Microsoft’s own APIs, as you’d expect.
VMware’s new product increases the amount of memory available to each VM to 3.6GB, support for shared network adapters and, VMware said, a performance hike for network and disk operations of up to 10 to 20 per cent. It also features automatic virtual start-up and shutdown, PXE provisioning for booting and installing operating systems into new virtual machines.
Both vendors say their products support Windows and Linux in VMs; VMware adds NetWare and FreeBSD. Microsoft’s VS is hosted only by Windows Server 2003, while GSX Server 3 can be hosted by a range of Windows and Linux OSes.
Analysts have indicated there is demand for Microsoft’s VS, which Microsoft hopes will spur migration from its ageing NT and 2000 software as companies seek to reduce the cost of upgrades and eliminate network heterogeneity. And Gartner reckons that enterprises considering VS should consider it strategic. However, Virtual Server won’t emerge as a finished product for several months so Gartner's advice on VMware is that enterprises should strongly consider VMware as a tactical solution.
In contract, VMware marketing VP Mike Mullany reckoned he didn’t see Microsoft and VMware as being in direct competition. He believed Microsoft sees virtualisation at the application level and as addressing the problem of migrating its users from NT4 and Windows 2000 to Windows Server 2003. VMware on the other hand he saw as being more focused on hardware-based virtualisation.
Conclusion
In the end though, virtualisation as a technique for server consolidation is bound to grow. Constraints on server space that will not allow the luxury of running one server per function. And with redundant hardware components, hardware that is becoming more reliable, and with upcoming multi-processor chips that will allow greater separation between VMs, virtualisation as a technique becomes more attractive.
Fortunately, you still have a choice of VM software too - VMware or Microsoft. We expect to be looking at both of these in more detail soon.