Virtual solutions

Microsoft solutions
Microsoft has two virtualisation products, Virtual PC 2004 for use on desktop PCs and Virtual Server 2005 for servers. Both are easy to install and use, and can be downloaded free. Linux as a guest OS. With the R2 release of Virtual Server 2005, Linux is now officially supported, with add-on tools for use with the open-source platform.

These products will continue to be developed and are increasingly being used by small businesses. They will be joined by a new implementation called Windows Server Virtualisation, which, like VMWare ESX Server, will be a ‘hypervisor’ solution. This means it can be installed directly onto a host server rather than on top of an existing OS, for enhanced performance and reliability.

Windows Server Virtualisation will be bundled with Longhorn, the next version of Windows Server, due out in 2007. It will be 64-bit only, require processors with virtualisation extensions and is aimed at big companies looking to virtualise production servers.

Other products
Among the smaller developers you’ll see a lot written about Xen Source and its open-source Xen virtualisation solution. Xen lacks the maturity of rivals VMWare and Microsoft, with most current implementations only able to host Linux, which even then has to be modified to run in a Xen VM – so-called para-virtualisation.

Xen, however, is included in the recently released Suse Enterprise Linux 10 distro from Novell and will also be in Red Hat Enterprise Linux 5. The latest implementation can also host off-the-shelf guests, including Windows, although only when run on processors with hardware virtualisation (see Virtual inside, later).

There are more specialised virtualisation products and technologies, such as operating system ‘containers’ where applications run in isolated environments within one operating system, and application virtualisation tools such as the Altiris Software Virtualization.

Instead of virtualising a whole PC, these use virtualisation to distribute and run applications. Microsoft recently bought into this use of the technology (through its acquisition of Softricity), as have other companies.

Virtual desktops
Virtualisation can also be applied to PC desktops. Host them in dedicated VMs running on a server and you get all the benefits of thin-client computing, but instead of a shared terminal server, each user gets their own virtual PC, accessible using cheap thin-client hardware.

VMWare is keen to promote this use of its virtualisation technology under its Virtual Desktop Infrastructure (VDI) initiative, which is gaining a lot of industry support. Wyse has introduced a VDI version of its S10 thin client, designed to act as a front end to virtual desktops hosted by a VMWare Server.

The S10 connects to the virtual PC using Microsoft’s RDP (Remote Desktop Protocol) with a feature Wyse calls “power on to work”, whereby you’re automatically connected to your virtual PC as soon as it’s switched on.

Special brokering and management software is required for this to happen, but there are lots of products to choose from, such as Virtual Desktop Connection Broker from Leostream, Propero Workspace and Clearcube Sentral. These products can be configured to connect users to the same dedicated PC each time or to allocate virtual machines dynamically based on user requirements and availability.

Virtual licensing
Virtualisation has crucial implications for software vendors that licence their products per CPU or per server. With open source it doesn’t matter, as you can install most Linux distros and many open-source applications on as many virtual machines as you want without buying additional licences.

However, there are exceptions and with proprietary software in particular you need to check the licensing terms to see if virtualisation is covered.

Most of the big-name developers have altered their terms to account for virtual deployment and many have afforded big concessions, including Microsoft.

Microsoft no longer requires the purchase of a licence for every stored Windows VM. Instead, licences are only required when a VM is turned on, and virtual machines running Windows can be moved between licensed servers without limitation.

Companies running Windows Server 2003 R2 are allowed up to four virtual machines per server at no extra cost. The Datacenter Edition of the next Longhorn implementation will allow unlimited virtual systems per machine. Other Microsoft products licensed by processor, such as SQL Server, Biztalk and ISA Server, can be used on multiple VMs. They are licensed for the number of virtual processors used, not physical processors on a host server.

With the efficient use of hardware and reasonable licensing terms, virtualisation really is a hot technology. No matter what size your company, it’s worth looking into.

Virtual inside
Chip makers Intel and AMD are doing their bit by building extra virtualisation functionality into their processors. Referred to as VT by Intel and AMD-V by rival AMD, the technology is essentially the same, but with small differences in implementation. To enable several virtual machines to share the same processor or processors, virtualisation vendors use what’s referred to as a Virtual Machine Monitor (VMM).

One of the things this does is broker operating system requests made to the privileged Ring 0 core of the processor, as defined in the original x86 architecture. Previously implemented in software, Intel VT and AMD-V add a hardware VMM on the processor itself, potentially enhancing performance and giving greater reliability through better virtual machine separation.

They also make life easier for both virtualisation developers and customers, as there’s no need to patch the VMM every time a new or updated guest operating system is released. On the downside virtualisation vendors have had to update their software twice to use these new hardware extensions because software written for one won’t work with the other.

However, the leading vendors do offer support for both Intel and AMD platforms. Customers also need to upgrade their processors to take advantage of the technology. For Intel that means the latest Pentium and Xeon chips, while for AMD it’s Revision F Opterons.

However, it’s worth remembering that you don’t have to buy new processors, PCs or servers to reap the benefits of virtualisation. VMWare, Microsoft and others continue to support existing processors using a software VMM and will do so for a long time to come.