Today, VMware has released the next version of its hypervisor: vSphere 4.1 is an incremental update to its low-level dedicated virtual host, with roots in the Linux codebase buried deep under man-centuries of coding effort by VMware’s virtualisation gurus. So what is it, and why should you care?

VSphere is the gadget which was offered as bootable from a USB key, so the whole of your host machine’s disk farm was available for guests: look inside an enterprise grade server and you can see the little internal USB sockets for this purpose.

I haven’t seen many setups that bother to go that far: most smaller businesses have trouble steeling themselves for a jump to a complete separation between compute resource and storage resource, so for them it is a relief that vSphere 4.1 can be installed on a single simple regular PC’s one lonely SATA hard drive, just as if it was an old-school operating system. Getting the 60 day free trial for small businesses as a proof of concept in this case doesn’t require a £20,000 Storage Area Network.

As always, you have to chop through the verbiage with the machete of righteous tight-fistedness to see what a small business gains from an update like this. VMware sent Raghu Raghuram over to the UK last week for a pre-release chat and I subjected him to the delights of an early morning breakfast in Smithfield Market, which didn’t faze him at all – we chatted about the usefulness of memory compression and the dubious take up of virtual machine host mobility over the beans and fried bread: I always think that blue-sky conversations about software enhancements to permit the management of 10,000 virtual machines from a single operator console are best done somewhere that real workers are clearly visible doing real work.

While most of our conversation was about the challenges that beset the very highest end of the virtualisation marketplace, I spotted a couple of points that make the small business trial definitely useful to help you understand what’s happening inside a virtual server.

One is that the memory footprint of a guest machine inside a vSphere 4.1 host has been reduced by 25%, by some clever-clogs memory compression by the hypervisor. So a candidate host machine which previously could only fit two guests inside the installed memory now has a fighting chance of hosting a third. The other is that vSphere 4.0 let you see and manipulate how much memory and processor each guest is permitted to monopolise, with little sliders: VSphere 4.1 adds storage bandwidth to that list.

In smaller businesses, I always find that the impact of more and faster storage is always the hardest thing to demo – and yet, it is also the change that has the biggest visible effect on daily operations. Being able to waggle a slider and demonstrate a guest machine job going quick, slow, quick quick slow, has to be a big plus.

I won’t try to delve into every last feature here: there will be more to come. I’d be interested to hear what other people think, though. If you download the trial, feel free to post your thoughts below.