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After a machine of mine became consumed by a project, I have been building a new set of disks latest for my use during new projects.  I always build my VPCs using differencing disk.  For those of you new to this concept, it allows you to build a disk off of a parent disk and all changes at that point will go to the new disk.  With the environment changing on us constantly with different releases of products, it is critical for you to get your project up quick.  Here is my example:

Differencing Disk Approach

As you can see, I am using sub-folders for all disks that build off of a parent.  So I have a disk for Windows XP SP2, then another built off of that for Office 2003.  Then SQL Server 2000, Visual Studio 2005, Core developer tools, and ASP.NET Web Projects.  When Office 2007 releases, I can create a sub-folder in the Windows XP 2003 directory and place a disk there.  When Vista comes out, I will create a new core folder.  When I need SQL Server 2005, I will build that off of the Office 2003 disk.  You can see the power of these disks.

Big Tip #1! - Building one project file that merges all disks

When I am ready to start a project, I build another difference disk on top of the disk you want to build from.  So if I had a new client that needed VS 2005, Office 2003, SQL 2000, and XP for a development environment, I would go to the lowest subfolder I wanted and choose that disk as the parent to the new disk.  After this is done, run the Virtual Disk Wizard and edit the new disk.  Choose to merge disks to new disk option and this will generate one disk for all the difference disks you have in your chain.  Now your project is separated from your build disk tree and you can place all the other disks on a dedicated hard drive just for building new projects. 

Big Tip #2!  - Mark as Read-Only

Just a friendly reminded to always mark your parent disks as Read-Only, that way you know you can't change them because someone else depends on their state.

Big Tip #3! - Build only what you need

Don't build all at once, only build what you need and always separate major products.  If you aren't using SQL Server 2005 yet, don't build it.

Big Tip #4 - Delete .vmc files of anything you are using as a parent

Don't tempt yourself to change a disk that is someone else's parent, just remove the settings file.

Final Tip! - New difference disks for updates

When building a SharePoint 2007 disks, I create a new one for the tech refresh that was a sub of the beta 2 disk.  This saved me so much time after I tried the upgrade 4 different times.  I would just delete the new TR disk and create another one and try again.


Posted on Monday, October 9, 2006 12:15 PM | Back to top

Comments on this post: Virtual PC Environments - Differencing Disk Tip

# re: Virtual PC Environments - Differencing Disk Tip
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How do you handle OS and app updates to the differenced disks? It seems you can't apply them at the highest level, you need to apply them at the lowest level. Or am I doing something wrong?
Left by Fred Beiderbecke on Oct 10, 2006 4:16 AM

# re: Virtual PC Environments - Differencing Disk Tip
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That is the most difficult problem with VPCs and disks. You can't change the parent once you have inherited from it.

I just always make a point to run windows update on any disk I create from the begining. Takes a few minutes but you are still saving time compared to building disks all day
Left by Jeff Julian on Oct 10, 2006 5:36 AM

# re: Virtual PC Environments - Differencing Disk Tip
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Dude, thanks for these tips. I've been setting up differencing disks lately and came across this, so now I'm setting things up from your tips.
Left by Dave Donaldson on Feb 20, 2007 1:28 PM

# re: Virtual PC Environments - Differencing Disk Tip
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So to create the disks in the sub-folders, do you make differencing disks of differencing disks?
Left by Steve Jackson on Mar 29, 2007 2:24 PM

# re: Virtual PC Environments - Differencing Disk Tip
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Yep, difference off a difference off, and you can build a nice structure. That way after you install windows on one office 2007 on another, you can then branch twice into SQL2K and SQL2K5.
Left by Jeff Julian on Mar 29, 2007 2:27 PM

# re: Virtual PC Environments - Differencing Disk Tip
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Hi, nice trick for managing so many VPC. Still, i'm wondering whats your host hard drive space requirements. Could you give us a rough idea how much space all those different virtual hard drives take?
Left by Aivo Jürgenson on Aug 02, 2007 9:57 AM

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