Saturday, October 21, 2006

Invirtus - VM Disk Optimiser

Like many in the IT industry, I use virtual machine technology for demonstrations, lectures and in classes, as well as to learn more about products in a safe environment. If you really screw up a VM, you can just recreate it, or roll back the changes to a known good state. I use VMware workstation on my home systems, as it's more efficient, more stable and has a richer set of functionality. I use Microsoft's VPC and VS products on my corporate laptop since I get so many VMs from MS that I need to use. One downside to using VMs is the size of the underlying virtual disks.  A simple installation of, say, Windows Server R2 takes over 2GB in disk space. Multiply this by 10 (I have that many VMs on my laptop), and disk space quickly becomes an issue.

I've been testing the Invirtus VM Optimizer 2.5 on some of my VPC virtual hard disks - and I'm quite impressed by this product. Here are two data points from this afternoon's testing:

  • My core VPC VM is a forest root domain controller in my test and demonstration forest. VMO reduced the size of the hard disk from 2,644,648KB to 1,458,567KB – just under half the size.  
  • The master VM Server R2 VM that I use to clone new VMs was next. This VM is setup, fully configured as a workgroup server with IIS and a few other services, and is ready to be sysprepped.  The before size was 2,788,043kb, and the after size was 1,526, 167. Again a savings over 1GB.

As should be obvious, shrinking a VM by 1GB makes for enormous savings in disk space, make transfers (from backup hard disk to main system, or from a laptop to classroom computers, etc) much much faster.

Now the less than good news:

  • VDO does not work on Vista VMs. I’ve got a Vista RC1 VM that does not compress. The error message is a tad misleading – it says that the ability to compress Vista won’t come till Vista goes RC. But I’m running it on RC1!
  • VDO Does not support difference disks. This is a real issue for me in my day job - where use Microsoft provided VMs as part of MOC training courses. The MOC course 7034A (Live Communications Server 2005) for example uses 18 VMs based on difference disks. These take up a total of around 35gb.  If the results here were what we saw with stand alone disks, this would be compelling evidence for use in justifying a site license. 
  • The price is high - US$169 for a single user version, and US$591 for a 5-user version.

So while there is a bit of bad news, this package is fantastic for those of us who use independent VMs for testing and demo purposes. If you build and use VMs on a regular basis, you should have this tool. But don't take my word for it - go to their download site and get the evaluation version. The evaluation version is fully functional, but timebombs after 14 days.


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