SWsoft has updated Virtuozzo, its virtualisation software, to work with 64-bit extended chips from AMD and Intel. The system allows administrators to make a single operating system function as multiple operating system instances that can be managed and rebooted independently.

Virtuozzo 2.6.2 for Linux now supports AMD's AMD64 and Intel's EM64T architectures, allow both 32-bit and 64-bit applications to run on a single hardware platform. The architectures, found in the AMD Opteron and Intel's Xeon server chips, have become a popular way of boosting performance, particularly for applications that need to address large amounts of memory.

SWsoft also makes a Windows Server version of Virtuozzo, released earlier this year, but this doesn't yet support 64-bit extended architectures. The company originally focussed its efforts on Linux-based Web hosting businesses, which use Virtuozzo to run multiple customers' operating systems on a single physical server.

Hosting companies such as Rackspace still form the core of SWsoft's market, but the company is using its Windows version to expand its enterprise clientele.

Virtualisation is getting to be big business; Virtuozzo competes with products such as EMC's VVMware, Microsoft's Virtual Server and Xen, an open-source project developed at Cambridge. Sharing hardware between dozens or hundreds of operating system instances is an efficient use of resources, simplifies management and allows for virtual servers to be easily migrated from one hardware platform to another with no downtime, the argument goes.

Intel is building Virtualization Technology into its newer chips, eliminating much of the processing overhead involved in the technique. Xen will be the first to support VT; AMD is expected to introduce its own hardware-based virtualisation scheme, code-named Pacifica, next year. Windows is unlikely to support VT or Pacifica until 2008, according to analysts.

Each vendor uses a slightly different approach to virtualisation. VMWare's approach is to virtualise, or simulate in software, a hardware platform for each operating system instance that is running; this entails a heavy overhead, however. "Paravirtualisation" schemes like Xen's do away with the hardware simulation and offer much better performance, but require the operating system to be modified - a requirement that will disappear with VT support.

Virtuozzo's approach is to virtualise the operating system rather than the hardware. In practice this means replacing the operating system's hardware abstraction layer with a customised one. This allows higher performance than full hardware virtualisation, but requires that all the operating system instances on a single physical server be of the same type, either Windows or Linux.

Virtuozzo scales up to 16-CPU systems with 64GB of RAM. The AMD64/EM64T compatible software is available now, and will be on display at the HP Technology Forum next month in Orlando, Florida. The software costs $999 per processor, with dual-core chips treated as a single processor for licensing

Early in September SWsoft released Linux-based virtualisation tools for HP's Integrity servers based on the high-end, 64-bit Itanium 2 processor.