Why virtualisation gets top marks

Major implementation highlights the benefits and pitfalls of going virtual

Many organisations are still experimenting with virtualisation to get the best from their IT infrastructure, but the Association of Teachers and Lecturers (ATL) has embraced the technology, and is nearing the end of a virtualisation programme that began in July 2005.

As reported in Computer Weekly earlier this month, the ATL has used VMware's ESX Server 2.5 platform to virtualise 17 core applications. Among these are Microsoft Exchange Server 2003 with Active Directory, Microsoft SQL Server 2000, Lotus Domino and an Oracle 9i 10g database.

Shifting these applications into a pool of virtualised computing resources has enabled the ATL to consolidate its servers at a ratio of five to one, reducing hardware and maintenance costs in the process.

The ATL has also gained the ability to recover quickly from system failures, as it can quickly move running applications between machines, and in and out of its disaster recovery environment, using VMware's VMotion tool.

Bernard King, systems architect at the ATL, said this ability was tested on 15 November last year when an important HP Proliant G4 server experienced power loss, knocking out the Exchange server. "During the night it rebooted, so it shut down and switched back on again in a previous state," said King.

But the ATL's virtual environment meant that within an hour the IT department had shifted the critical server applications onto another machine, and located the hardware fault inside the motherboard.

The server consolidation also means that the ATL now has a pool of spare servers that it is starting to redeploy for network load balancing on its website, said King.

The ATL has also found that virtualisation makes more demands on the storage area network (San), and has begun reorganising the San to make it bigger and more robust.

"VMware requires a different way to balance the load, as you have multiple machines accessing the hard disc. So you are constantly having to restructure the San," said King. The ATL has added a second San for backup purposes.

One key issue the ATL has been forced to confront is licensing. Under many licences, applications are tied to particular servers, so moving them around can break the terms of existing agreements. This has caused the ATL to shelve moving some systems over to the virtual environment, including a document management system.

"Licensing can be a sticking point when deciding whether or not to virtualise. With our document management system, the supplier was reluctant to support it. They were going to put us on a support contract that would be more costly so we decided not to virtualise it," said King.

However, both Microsoft and Oracle have agreed to ATL running their applications over multiple machines, licensing them per user rather than per CPU core.

Application support has also changed, because some of the ATL's suppliers prefer the ATL to send DVDs with virtual machines running the application to help fix any errors. This was the case with both Tridian, the ATL's content management supplier, and Verity.

But King and the ATL are far from finished with virtualisation technology. The plan for this year includes virtualising key Blackberry servers, an Autonomy Idol system, and 64-bit Exchange Server 2005.

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