With the launch of VMware's Workstation 5, the company has focused on the needs of independent software vendors (ISVs). ISVs need multiple images for cross-platform testing, and also the ability to take a snapshot at a particular point in the development process, so that if a new piece of code proves not to be the right way forward, they can backtrack.

One user, Dave Parsons, software development manager for 110-strong ALG Software, explained how his company has been using the product since the early beta days.

He added that ALG has also been instrumental in helping VMware decide what to put into the product. "They've taken a lot of our suggestions for this product" said Parsons.

Parsons said that ALG had been using VMware extensively for QA and development. "Its always been a good product and been part of our day-to-day environment," he said.

Version 5 makes our lives easier though," said Parsons.

He talked about the first of the three key features that VMware has introduced into with version 5, multiple snapshots, which allow users to take multiple point-in-time snapshots of running virtual machines and revert back to any snapshot with the click of a button.

"Multiple snapshots means we can work on something and go back to a particular point in time using multiple snapshots, to work through the code or configuration. That's why it's extremely useful for us," said Parsons.

"Yesterday, I was setting up a Linux server for testing. I had to load several different packages and I took a snapshot after installing each package -- Apache, MySQL and so on -- so I could go back if the setup was wrong. It gives you greater granularity because it doesn't commit everything as the previous version did. Instead, you can branch them and revert to previous versions."

Parsons gave a second example. "There was an internal Web server I set up. I wanted to check two different versions of PHP, versions four and five. It meant I could decide which I wanted to use without destroying the other. And when developing and testing, for instance with Oracle, we can apply a patch using a branched snapshot without having to set up two separate virtual machines."

Parson said that VMware Workstation 5 could be useful outside development environments too. "Our IT team want to use it to do things such as sorting out a problem with the Exchange server. They could replicate an issue in a VM, and if that wasn't the problem, they could roll back and try something else."

A second new feature is linked clones. "This works with snapshots nicely," said Parsons. "I have a base image for installing our software -- three linked clones -- one in production and two in development, all looking into the one base image.

"This saves a lot of disk space -- about 2GB per image and per software version. Now this means we can keep a base image and put incremental versions of our software on it -- 2.02 then 2.03, for instance -- without destroying the common base image. Disk space may be cheap but this makes maintenance easier."

"Backups are easier because of the VM image size savings. One thing we haven't tried yet is to link to a network share as a base image, though I believe that's possible. We'd look to create a base image for each OS and allow the team to develop software on top of that. It simplifies management too as you can freeze a single image and don't have to push it around the network."

Parsons added that, "You can create linked images on top of linked images, which saves a lot of disk space. All mine used to add up to 100GB and I can rationalise them down to something a lot more manageable and portable."

Also key for Parsons is the new team system, which allows users to connect multiple virtual machines with configurable network segments to simulate and test issues such as network bandwidth and packet loss rate.

"While we do have real machines set up," said Parsons, "QA testing is about functionality, so our developers may have three or four machines set up as clients, a Web server and database server, all replicating a real world scenario. The team feature means they can then plug things in and out to replicate that. It gives us multiple options to recreate situations that our customers face."

"We've also used VLAN segments which mean we can test using bandwidth throttling. We did that to emulate different types of network such as an E1 or ISDN, and that allows us to do network performance monitoring. I was able to plot graphs that allowed me to see what would happen in real life.

"It was a simpler way to do that rather than have four machines with a network analyser sitting in a room. You still need do that of course, but this allows you to do it off-site, wherever you are on a single machine. It also gives us flexibility to try things out so that if the kit we need to do real world testing is in use elsewhere."

Parsons ranked the new features in terms of their usefulness starting with multiple snapshots, then linked clones followed by teams. "I can see that there is overlap but they work well together," said Parsons.

And he still had suggestions for the next version including an additional module that allows you to create a VMware ACE package. We also want to see support for Windows clusters -- we've done it but it's not officially supported. And they need to catch-up with things like supporting latest version of Linux and Solaris 10. It's becoming more important to us because we're doing more cross-platform work."