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The eternal arguement is, “Which is the better option; Original Virtual machines, compact templates or OVF?” Certainly each has it’s own advantages and disadvantages. The one consideration, immeadiately is size.

From time to time I am asked if there were any benefit to templating vs. cloning vs. storing a VM in OVF format. So I thought I’d use the resources at my disposal from my VDC kit and give it a go.

We all know that it can take longer to create a compact template than a normal template. However on the flip side, a compact template normally deploys more quickly. We also know that storing a template in compact format may possible save us room in storage depending on how much free space there is in the vmdk(s).

I took our normal class VM (2GB hard drive) and created a compact template and then exported it to OVF format virtual appliance. Then I compared the resulting sizes of each. OK, I was not going for “exact” numbers, just general indications of size (see attached graphics).

1. Original VM took slightly more than 2GB to store (as would the resulting normal template)
2. Compact template took slightly more than 1GB to store
3. OVF virtual appliance took slightly less than 500MB to store

This seems to indicate that there is a significant space savings to be had if you store your VMs as OVF virtual appliances instead of templates or clones. Now this does not take in to account the time it takes to create and deploy VMs from OFV vs. templates, but it did get me to thinking. I would like to try this again with a larger vmdk and with more actual data saved to the vmdk, but at the moment I have neither the time nor the resources to do so.

Original Virtual Machine
Compact Template
OVF

Aaron Thorpe, a fellow VCI said, It’s definitely something interesting to consider. One thing we discovered during a class discussion was that if you create a compact template, it converts the VMDK to a thin disk. However all new VMs created from this template will also use a thin disk. We were concerned that this may hurt disk performance of all future VMs deployed from the template, but we did not have time to test thoroughly.

I wonder if anyone has written a comparative whitepaper…

That said, I think that templates have more benefits than OVF if we are talking about VMware features rather than just saving space. Cloning still allows us to use the “Guest Customization Wizard”. I can’t do this to an OVF machine.