Volume Shadow Copy – How to Use VSS for Backups on Windows Server 2003

So in the spirit of reinventing the wheel, I present to you Tomalak's excellent script (see above) but completely rewritten in Powershell!!! The main reason I did this was to evangelise the awesome powers of Powershell, but also because I despise vbscript with my entire being.

It's mostly feature to feature identical, but I did implement some things a little differently for various reasons. The debugging output is definitely more verbose.

One very important thing to note is that this version detects the OS version and bitness and calls the appropriate version of vshadow.exe. I've included a chart below to show which versions of vshadow.exe to use, where to get them, and what to name them.

Here's the usage info:

VssSnapshot.ps1

Description:
  Create, mount or delete a Volume Shadow Copy Service (VSS) Shadow Copy (snapshot)

Usage:
  VssSnapshot.ps1 Create -Target <Path> -Volume <Volume> [-Debug]
  VssSnapshot.ps1 Delete -Target <Path> [-Debug]

Paremeters:
  Create  - Create a snapshot for the specified volume and mount it at the specified target
  Delete  - Unmount and delete the snapshot mounted at the specified target
  -Target - The path (quoted string) of the snapshot mount point
  -Volume - The volume (drive letter) to snapshot
  -Debug  - Enable debug output (optional)

Examples:
  VssSnapshot.ps1 Create -Target D:\Backup\DriveC -Volume C
  - Create a snapshot of volume C and mount it at "D:\Backup\DriveC"

  VssSnapshot.ps1 Delete -Target D:\Backup\DriveC
  - Unmount and delete a snapshot mounted at "D:\Backup\DriveC"

Advanced:
  VssSnapshot.ps1 create -t "c:\vss mount\c" -v C -d
  - Create a snapshot of volume C and mount it at "C:\Vss Mount\C"
  - example mounts snapshot on source volume (C: --> C:)
  - example uses shortform parameter names
  - example uses quoted paths with whitespace
  - example includes debug output

Here's the script:

# VssSnapshot.ps1
# http://serverfault.com/questions/119120/how-to-use-a-volume-shadow-copy-to-make-backups/119592#119592

Param ([String]$Action, [String]$Target, [String]$Volume, [Switch]$Debug)
$ScriptCommandLine = $MyInvocation.Line
$vshadowPath = "."

# Functions
Function Check-Environment {
  Write-Dbg "Checking environment..."

  $UsageMsg = @'
VssSnapshot

Description:
  Create, mount or delete a Volume Shadow Copy Service (VSS) Shadow Copy (snapshot)

Usage:
  VssSnapshot.ps1 Create -Target <Path> -Volume <Volume> [-Debug]
  VssSnapshot.ps1 Delete -Target <Path> [-Debug]

Paremeters:
  Create  - Create a snapshot for the specified volume and mount it at the specified target
  Delete  - Unmount and delete the snapshot mounted at the specified target
  -Target - The path (quoted string) of the snapshot mount point
  -Volume - The volume (drive letter) to snapshot
  -Debug  - Enable debug output (optional)

Examples:
  VssSnapshot.ps1 Create -Target D:\Backup\DriveC -Volume C
  - Create a snapshot of volume C and mount it at "D:\Backup\DriveC"

  VssSnapshot.ps1 Delete -Target D:\Backup\DriveC
  - Unmount and delete a snapshot mounted at "D:\Backup\DriveC"

Advanced:
  VssSnapshot.ps1 create -t "c:\vss mount\c" -v C -d
  - Create a snapshot of volume C and mount it at "C:\Vss Mount\C"
  - example mounts snapshot on source volume (C: --> C:)
  - example uses shortform parameter names
  - example uses quoted paths with whitespace
  - example includes debug output
'@

  If ($Action -eq "Create" -And ($Target -And $Volume)) {
    $Script:Volume = (Get-PSDrive | Where-Object {$_.Name -eq ($Volume).Substring(0,1)}).Root
    If ($Volume -ne "") {
      Write-Dbg "Verified volume: $Volume"
    } Else {
      Write-Dbg "Cannot find the specified volume"
      Exit-Script "Cannot find the specified volume"
    }
    Write-Dbg "Argument check passed"
  } ElseIf ($Action -eq "Delete" -And $Target ) {
    Write-Dbg "Argument check passed"
  } Else {
    Write-Dbg "Invalid arguments: $ScriptCommandLine"
    Exit-Script "Invalid arguments`n`n$UsageMsg"
  }


  $WinVer = ((Get-WmiObject Win32_OperatingSystem).Version).Substring(0,3)
    Switch ($WinVer) {
    "5.2" {
      $vshadowExe = "vshadow_2003"
      $WinBit = ((Get-WmiObject Win32_Processor)[0]).AddressWidth
    }
    "6.0" {
      $vshadowExe = "vshadow_2008"
      $WinBit = (Get-WmiObject Win32_OperatingSystem).OSArchitecture
    }
    "6.1" {
      $vshadowExe = "vshadow_2008R2"
      $WinBit = (Get-WmiObject Win32_OperatingSystem).OSArchitecture
    }
    Default {
      Write-Dbg "Unable to determine OS version"
      Exit-Script "Unable to determine OS version"
    }
  }

  Switch ($WinBit) {
    {($_ -eq "32") -or ($_ -eq "32-bit")} {$vshadowExe += "_x86.exe"}
    {($_ -eq "64") -or ($_ -eq "64-bit")} {$vshadowExe += "_x64.exe"}
    Default {
      Write-Dbg "Unable to determine OS bitness"
      Exit-Script "Unable to determine OS bitness"
    }
  }

  $Script:vshadowExePath = Join-Path $vshadowPath $vshadowExe
  If (Test-Path $vshadowExePath) {
    Write-Dbg "Verified vshadow.exe: $vshadowExePath"
  } Else {
    Write-Dbg "Cannot find vshadow.exe: $vshadowExePath"
    Exit-Script "Cannot find vshadow.exe"
  }

  Write-Dbg "Environment ready"
}

Function Prepare-Target {
  Write-Log "Preparing target..."
  Write-Dbg "Preparing target $Target"


  If (!(Test-Path (Split-Path $Target -Parent))) {
  Write-Dbg "Target parent does not exist"
  Exit-Script "Invalid target $Target"
  }
  If ((Test-Path $Target)) {
    Write-Dbg "Target already exists"
    If (@(Get-ChildItem $Target).Count -eq 0) {
      Write-Dbg "Target is empty"
    } Else {
      Write-Dbg "Target is not empty"
      Exit-Script "Target contains files/folders"
    }
  } Else {
    Write-Dbg "Target does not exist. Prompting user..."
    $PromptYes = New-Object System.Management.Automation.Host.ChoiceDescription "&Yes", "Create target folder"
    $PromptNo = New-Object System.Management.Automation.Host.ChoiceDescription "&No", "Do not create target folder"
    $PromptOptions = [System.Management.Automation.Host.ChoiceDescription[]]($PromptYes, $PromptNo)
    $PromptResult = $Host.UI.PromptForChoice("Create folder", "The target folder `"$target`" does not exist.`nWould you like to create the folder?", $PromptOptions, 0) 
    Switch ($PromptResult) {
      0 {
        Write-Dbg "User Accepted. Creating target..."
        $Null = New-Item -Path (Split-Path $Target -Parent) -Name (Split-Path $Target -Leaf) -ItemType "Directory"
      }
      1 {
        Write-Dbg "User declined. Exiting..."
        Exit-Script "Target does not exist"
      }
    }
  }
  Write-Log "Target ""$Target"" ready"
  Write-Dbg """$Target"" ready"
}

Function Create-Snapshot {
  Write-Log "Creating snapshot..."
  Write-Dbg "Creating snapshot of $Volume"
  $Cmd = "$vshadowExePath -p $Volume"
  $CmdResult = Run-Command $Cmd -AsString

  Write-Dbg "Snapshot created successfully"

  $SnapshotID = $CmdResult -Match 'SNAPSHOT ID = (\{[^}]{36}\})'
  If ($SnapshotID) {
    $SnapshotID = $Matches[1]
    Write-Dbg "SnapshotID: $SnapshotID"
    Write-Log "Snapshot $SnapshotID created"
  } Else {
    Write-Dbg "Unable to determine SnapshotID"
    Exit-Script "Unable to determine SnapshotID"
  }

  Return $SnapshotID
}

Function Mount-Snapshot ($SnapshotID) {
  Write-Log "Mounting snapshot..."
  Write-Dbg "Mounting $SnapshotID at ""$Target"""

  $Cmd = "$vshadowExePath `"-el=$SnapshotId,$Target`"" #Must use escaped quotes because Invoke-Expression gets all weird about curly braces
  $CmdResult = Run-Command $Cmd

  Write-Log "Snapshot $SnapshotID mounted at target ""$Target"""
  Write-Dbg "$SnapshotID mounted at ""$Target"""
}

Function Delete-Snapshot {
  Write-Log "Deleting snapshot..."
  Write-Dbg "Deleting snapshot at target ""$Target"""

  $SnapshotID = Get-SnapshotIdbyTarget

  $Cmd = "$vshadowExePath `"-ds=$SnapshotId`""
  $CmdResult = Run-Command $Cmd

  Write-Log "Snapshot $SnapshotID deleted at target ""$Target"""
  Write-Dbg "$SnapshotID deleted at ""$Target"""
}

Function Get-SnapshotIdbyTarget {
  Write-Dbg "Finding SnapshotID for $Target"

  $Cmd = "$vshadowExePath -q"
  $CmdResult = Run-Command $Cmd -AsString

  $TargetRegEx = '(?i)' + $Target.Replace('\','\\') + '\\?\r'
  $Snapshots = ($CmdResult.Split('*')) -Match $TargetRegEx | Out-String

  If ($Snapshots) {
    $Null = $Snapshots -Match '(\{[^}]{36}\})'
    $SnapshotID = $Matches[0]
  } Else {
    Write-Dbg "Unable to determine SnapshotID for target $Target"
    Exit-Script "Unable to determine SnapshotID"
  }  

  Write-Dbg "SnapshotID: $SnapshotID"

  Return $SnapshotID
}

Function Run-Command ([String]$Cmd, [Switch]$AsString=$False, [Switch]$AsArray=$False) {
  Write-Dbg "Running: $Cmd"

  $CmdOutputArray = Invoke-Expression $Cmd
  $CmdOutputString = $CmdOutputArray | Out-String
  $CmdErrorCode = $LASTEXITCODE

  If ($CmdErrorCode -eq 0 ) {
    Write-Dbg "Command successful. Exit code: $CmdErrorCode"
    Write-Dbg $CmdOutputString
  } Else {
    Write-Dbg "Command failed. Exit code: $CmdErrorCode"
    Write-Dbg $CmdOutputString
    Exit-Script "Command failed. Exit code: $CmdErrorCode"
  }

  If (!($AsString -or $AsArray)) {
    Return $CmdErrorCode
  } ElseIf ($AsString) {
    Return $CmdOutputString
  } ElseIf ($AsArray) {
    Return $CmdOutputArray
  }
}

Function Write-Msg ([String]$Message) {
  If ($Message -ne "") {
    Write-Host $Message
  }
}

Function Write-Log ([String]$Message) {
  Write-Msg "[$(Get-Date -Format G)] $Message"
}

Function Write-Dbg ([String]$Message) {
  If ($Debug) {
    Write-Msg ("-" * 80)
    Write-Msg "[DEBUG] $Message"
    Write-Msg ("-" * 80)
  }
}

Function Exit-Script ([String]$Message) {
  If ($Message -ne "") {
    Write-Msg "`n[FATAL ERROR] $Message`n"
  }
  Exit 1
}

# Main
Write-Log "VssSnapshot started"
Check-Environment

Switch ($Action) {
  "Create" {
    Prepare-Target
    $SnapshotID = Create-Snapshot
    Mount-Snapshot $SnapshotID
  }
  "Delete" {
    Delete-Snapshot
  }
}

Write-Log "VssSnapshot finished"

Here are the vshadow.exe versions to use:

1. Windows 2003/2003R2
   • Volume Shadow Copy Service SDK 7.2
   • x86: C:\Program Files\Microsoft\VSSSDK72\TestApps\vshadow\bin\release-server\vshadow.exe
     • Rename to: vshadow_2003_x86.exe
   • x64: I have not been able to locate an x64 version of vshadow.exe for Windows 2003 x64
2. Windows 2008
   • Windows SDK for Windows Server 2008 and .NET Framework 3.5
   • x86: C:\Program Files\Microsoft SDKs\Windows\v6.1\Bin\vsstools\vshadow.exe
     • Rename to: vshadow_2008_x86.exe
   • x64: C:\Program Files\Microsoft SDKs\Windows\v6.1\Bin\x64\vsstools\vshadow.exe
     • Rename to: vshadow_2008_x64.exe
3. Windows 2008R2
   • Microsoft Windows SDK for Windows 7 and .NET Framework 4
   • x86: C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin\vsstools\vshadow.exe
     • Rename to: vshadow_2008R2_x86.exe
   • x64: C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin\x64\vsstools\vshadow.exe
     • Rename to: vshadow_2008R2_x64.exe