Not to put too fine a point on it, but as decades go, the 2000s sucked. It's hard to imagine a worse beginning than the dot-com bust followed by September 11. And the Great Recession as a grand finale? Yet somehow technology kept barreling along. In business, the shift from client-server to web, from proprietary and expensive to open and commoditised, was stunning in its swiftness. The impact on IT was a little more chaotic than we might have liked, but plummeting costs had the effect of driving technology into every corner of the enterprise. Predictions of IT's irrelevancy proved exactly wrong. Looking back on the '00s, I found it pretty easy to pick the five technologies I thought had the greatest impact on business. Remember, these weren't invented during the decade, but all of them most certainly came into their own in the '00s. 1. Linux. If you were going to name the '00s after any single technology, you might as well call it the Linux decade. The first Linux kernel was released in 1991, but mainstream enterprise adoption of Linux was decidedly a '00s thing. Not only did Linux open up a whole new role for x86 hardware, it changed the economics and development model of the software business forever. 2. XML. First recommended to the W3C in 1998, XML didn't really get rolling until 2002 or so. Today XML is the universal standard for document and data exchange, enabling everything from enterprise application integration to RSS. Every major commercial DBMS now claims "native XML" capability. The degree to which different business systems can exchange data smoothly may be pathetic compared to what it should be in 2009, but XML gets much of the credit for the inroads we've made so far. 3. Server virtualisation. I have a vivid memory of Diane Greene, then CEO of VMware, sitting in InfoWorld's offices in 2004 explaining how virtualisation worked. It was an "oh wow" rather than an "a ha" moment, although I can't pretend to have guessed the impact the technology would have. The idea of divvying up one server into many virtual machines seemed more like an academic exercise than a commercial boon, until I understood how desperately underutilised most servers were. We may never again witness anything like the pace at which server virtualisation has been adopted. Enterprise IT normally doesn't jump on anything that fast. 4. Rich Internet applications. A grab bag of technologies, including AJAX and Flash, enabled web apps to replace client-server applications across the enterprise. As long as programmers avoided browser-specific features, new application versions no longer needed client upgrades — which, among other things, allowed software as a service to bloom. The shift to web apps also democratised programming, fostering lightweight development using scripting languages. 5. Storage area networking. Pooled, block-addressable storage spread across multiple storage arrays connected via FibreChannel was a novel idea at the outset of this decade. SANs offered fast access to big storage, improved reliability and availability, and awesome scalability. Separating enterprise data and putting it on its own reliable high-speed network also made server failures far less critical. Sorry, did I leave out the iPhone? Well, it's not an enterprise technology — yet. But there are many viable alternatives to choose from in building your own list. Take blade servers, for one. Or VoIP. Or network attached storage. Or ... Windows XP? If the '80s was the decade of the PC, and the '90s was the decade of the internet, then the one thing the '00s lacked was a big, single, defining technology. Though you can't call it a technological advance, I think of the '00s as the decade of data. Thanks in part to Enron, we compulsively saved petabytes of the stuff. And there it sits, while at the same time, we have tons of cheap surplus computing power — spreading from underutilitsed CPUs in the datacentre to server farms in the cloud. With luck, the 2010s will be the decade in which we finally figure out how to put the two together on an unprecedented scale.