Delete differential images based on available free space

Overview

The instructions presented in this topic demonstrate how you would use VBScript to delete the oldest differential images in a backup set based on the amount free space available on the backup drive.

In the following example we generate a VBScript source file that, if necessary, creates 5 GB of free space on the target drive by deleting the oldest differential images before running the current differential.

To delete differential images based on available free space

1. In the Backup Definition Files tab, right-click a backup definition file and choose Generate a VB Script File from the shortcut menu.
   
   
   
   The VBScript generation dialog box appears.
   
   

2. Leave the options as defaults but change the file name for clarity.

3. Select the VBScript Files tab, right-click the new file and select Edit from the shortcut menu.
   
   
   
   The VBScript file opens in the system default text editor, generally this is Notepad.

4. For clarity, switch off word wrap. In notepad, choose Edit > Word Wrap.
   
       

5. Edit the file in Notepad as follows:
   
   Before the line:
   
   ' Do the backup
   
   Copy and paste the following:
   
   ' Create 5GB free space
   CreateSpace "N:\Backups", 5 * 1024

   Note The number 5 represents the number of GB of free space you want to create to ensure you have enough space before running the backup. Change 'N:\Backups' to the path of your image.

    

6.  At the end of the file copy and paste the following code:
   
   Function CreateSpace(ByVal drvPath, MB)
   While GetFreeSpaceMB(drvPath) < MB
   If DeleteOldestFile(drvPath) = false Then
       Exit Function
   End If
   Wend
   End Function
   
   Function GetFreeSpaceMB(ByVal drvPath)
   Dim objFSo, d
   Set objFSo  = CreateObject("Scripting.FileSystemObject")
   If Not objFSO.FolderExists(drvPath) Then
   ' return a big number if the folder doesn't exist
   GetFreeSpaceMB = 1000 * 1024 * 1024
   Exit Function
   End If
   Set d = objFSo.GetDrive(objFSo.GetDriveName(drvPath))
   GetFreeSpaceMB = d.FreeSpace/ (1024 * 1024)
   End Function
   
   Function DeleteOldestFile(ByVal drvPath)
   Dim objFSo, colFiles , dtmOldestDate, strOldestFile, objFolder, objFile  
   Set objFSo = CreateObject("Scripting.FileSystemObject")
   Set objFolder = objFSO.GetFolder(drvPath)
   Set colFiles = objFolder.Files
   dtmOldestDate = Now
   
   For Each objFile in colFiles
   If objFile.DateLastModified < dtmOldestDate _
   AND Left(Right(objFile.Path, 11), 2) <> "00" _
   AND Right(objFile.Path, 6) = ".mrimg" Then
       dtmOldestDate = objFile.DateCreated
       strOldestFile = objFile.Path
   End If
   Next  
   
   If strOldestFile <> ""  Then
   objFSO.DeleteFile strOldestFile
   DeleteOldestFile = true
   Else
   DeleteOldestFile = false
   End If
   End Function

7. Save the file.

8. Execute or schedule the VBScript source file in exactly the same way as a backup definition file. See Schedule backups.