In the year or so since VMware released VMware Infrastructure 3.0 (VI3), it has come to be viewed as a watershed event in virtualisation. Building upon the reliability of the VMware ESX 2.5 hypervisor, VI3 and its sophisticated VM management tools brought virtualisation firmly into the IT mainstream. The recent upgrade to ESX Server 3.5 and VirtualCenter 2.5 doesn't equal the leap to VI3, but it does add a few features that will definitely come in handy for any virtualisation implementation.

These features are generally focused on easing the maintenance burden imposed by a virtualised infrastructure. Virtualisation promises to make server management intrinsically simpler, but as with many things in IT, it doesn't hit every target. Addressing some important pain points, VMware has added features such as patch management (Update Manager), live migration of VM disks (Storage VMotion), and a capacity planning wizard (Guided Consolidation) to the suite. Each of these new features fills a gap in the overall picture, and for the most part, does so quite well.

It's certainly true that many IT shops will build their first VMware implementation on ESX 3.5 and VirtualCenter 2.5, and will never have seen their predecessors, but by the same token, many current VI3 shops will be upgrading to the new revs as soon as possible to leverage the new features. To that end, my testing included not only brand-spanking-new ESX installations, but also -- the best possible test of any software release -- production upgrades.

The upgrade dance

Building VMware ESX hosts from scratch is as simple as it gets. Burn an ISO, insert into a server, boot from the CD, click OK a few times, and then add that host in the VMware Infrastructure Client. Configure the network, storage, and licensing, and that's essentially it. You can even reduce those steps if you PXE boot the VMware installer. Upgrading a host from ESX 3.0 to ESX 3.5 is actually simpler than building a new host, and requires very little downtime for the host. If your existing infrastructure is built properly, it means zero downtime for production VMs.

The first overall step to upgrading the whole infrastructure is to upgrade VirtualCenter (VC). Previous versions of VirtualCenter used MSDE (Microsoft SQL Desktop Engine) as the default database, but VMware's recommendation was to use the full-blown Microsoft SQL Server or Oracle Database to handle the database tasks. VC2.5 does away with the legacy MSDE, instead bundling Microsoft SQL Server 2005 Express Edition. This is a better database platform than MSDE, but is still designed for smaller implementations. In many production VMware environments, this is all that's necessary -- a welcome change from the previous iteration.