Added check, if folder already exists

Backup2ExternalHD.ps1

@@ -39,11 +39,23 @@ function Backup-Data($SourcePath,$BackupPath){
     Write-Host("  Backup-Data-Size: $foldersize (free: $free)")
     if ($foldersize -lt $free){
       $Destination = $BackupPath+"\"+$f  
-      Write-Host("  Source-Path: $Source")
-      Write-Host("  Target-Path: $Destination")
-      Copy-Dir -Source $Source -Destination $Destination
+      if (Test-Path -Path $Destination){
+        Write-Host("  Target folder exists...checking size")
+        $copysize = (Get-ChildItem -path $Destination -Recurse | Measure-Object -Property Length -sum).Sum / 1Gb    
+      } else {
+       $copysize = 0
+      }          
+      if ($foldersize -ne $copysize){
+        Write-Host("  Source-Path: $Source")
+        Write-Host("  Target-Path: $Destination")
+        #Copy-Dir -Source $Source -Destination $Destination
+      } else {
+        Write-Host("  Skipping $Source, as it is already available on destination with identical size.")
+      }
+      
       if ($move){
-        Remove-Item -Recurse -Force $Source
+        Write-Host("  Finally cleaning up after move")
+        #Remove-Item -Recurse -Force $Source
       }
     } else {
       Write-Host("ERROR: Not enough free space on Backup-Drive!")