Coding Corner: Compacting a virtual hard disk

Coding Corner: Compacting a virtual hard disk

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Today I am going to go over a basic script for compacting a virtual hard disk.  This script creates a virtual hard disk object from a string that points to the virtual hard disk file (in the script this information is provided as a command line parameter).  The script then executes the 'compact' method - which returns a VMTask object.  We can then use this VMTask object to monitor the progress of the compaction:

'Script Begins

On Error Resume Next

'Connect to Virtual Server and check for failure
Set virtualServer = CreateObject("VirtualServer.Application")
If Err.number <> 0 Then error("Failed to connect to Virtual Server")

'Connect to virtual hard disk (provided as command line parameter) and check for failure
Set aVirtualHardDisk = virtualServer.GetHardDisk(WScript.Arguments(0))
If Err.number <> 0 Then error("Failed to connect to virtual hard disk")

'Start compaction process and check for failure
Set compactionTask = aVirtualHardDisk.Compact
If Err.number <> 0 Then error("Failed to compact virtual hard disk")

'Display task description
wscript.echo compactionTask.Description

'Loop waiting for task completion - and display status
while not compactionTask.isComplete
   wscript.echo "Compaction is " & compactionTask.PercentCompleted & "% complete"
   WScript.Sleep 2000

wscript.echo "Compaction complete"

'Pause before exiting
WScript.Sleep 5000

'Generic error handler
sub error(message)

   wscript.echo message
   wscript.echo Err.Description
   WScript.Sleep 5000
end sub

'Script Ends

As there are a couple of areas where you could hit a problem - I have put in some basic error handling to explain why things fail.  Also - it should be noted that while this script will request that the virtual hard disk is compacted - the actual compaction is done by Virtual Server.  This means that if you close the command prompt window while the script is running - Virtual Server will continue to compact the virtual hard disk in the background.


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  • Please add 1 and 3 and type the answer here:
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  • Will this scripting be added to future release of Virtual PC anytime soon?
  • To make this a little more user friendly, add something like this:

    'Check for CScript
    If Not IsCScript() Then
    Wscript.Echo Wscript.ScriptName & " must be run with CScript."
    Wscript.Quit 1
    End If

    ' IsCscript - Checks CScript vs. WScript
    ' Date Name Comment
    ' ------ ------- -----------------------------------------------------------------
    ' 020507 CGL Created
    Function IsCScript()
    Dim objRegExp
    Set objRegExp = New RegExp
    objRegExp.IgnoreCase = true
    objRegExp.Pattern = "cscript.exe$"
    IsCScript = objRegExp.Test(WScript.FullName)
    Set objRegExp = Nothing
    End Function
  • Raymond -

    We are aware of the customer demand for this - however I do not tend to talk about future releases on this blog.

    Christopher -

    Yes - this is a good idea, however I try to keep my scripts as short as possible when I am posting them to my blog.

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