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My coworker Scott Hanselman recently blogged about his use and experience with the tool Invirtus VM Optimizer. The tool worked well for Scott and his dynamic disk MS Virtual PC images so I looked at how it could improve my fixed disk images. The site didn't reveal anything on improvment for fixed disks so I emailed support at Invirtus to ask about it:
I’m trying to understand how your product would work with a MS VPC that is utilizing the “Fixed Disk” feature. Since the VPC size is fixed will Optimizer shrink it to the smallest size and leave the image unusable (since it won’t don’t dynamically grow)? Or will Optimizer allow me to specify a buffer beyond the optimized size to ensure the VPC doesn’t run out of space?
The reply was:
Optimizer will work with a fixed disk in that it will increase the available free space to the maximum available. But, you cannot shrink the disk itself.
While writing test cases, on the side I converted a fixed disk image to a dynamic disk to see if Optimizer could decrease the 6.3 GB size. The attempt resulted in a slightly LARGER VPC size (6.4 GB). After scratching my head for a while I then emailed support to ask why:
I used your tool with a MS VPC that was a dynamic disk of 6.3 GB. After running the tool the disk ended up being a little over 6.4 GB. The VPC image was VERY clean prior to running of the tool (fresh Server 2003 OS install, SQL 2000, installed two Web Services and a few web sites). Am I missing something or is the tool primarily used for MS VPC bloat that is caused over time VPC? Why did the size go up?
The reply was:
In VM Optimizer we include a tool called Freespace.exe. Freespace.exe goes sector by sector and cleans the whitespace. This means that every sector on your disk is touched and when that happens on a virtual disk the size of the disk expands. However, in a dynamically expanding scenario the size will reduce quite substantially and in your fixed disk scenario the disk will remain approx. the same or grow just slightly.
So, no special magic here for me and my situation. It makes sense; you can't squeeze blood out of a turnip. For performance reasons, I converted a 6.3 GB virtual disk image to a 10.1 GB fixed disk image but the caveat is that copying and network transfer a bit painful. I'm assuming that the 3.8 GB difference is free space. My test environment doesn't need this much free space, 1 GB would be enough. At this point I think the only way to get my fixed disk smaller is to specify the free space when converting from dynamic to virtual. Does anybody know a trick for this? Am I looking at a feature request?
Update 6/19: I contacted Ben the Virtual PC Guy to see if he had any tricks up his sleeve for downsizing the free space in a fixed disk and he responded with: "We do not provide a way to change the maximum size of a virtual hard disk today. If you want to do this you will need to create a new virtual hard disk - at your desired size - and then use a tool like Symantec Ghost to transfer the data to the new virtual hard disk." |
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