Disk2VHD scheduled backup script

Question

I'm using such simple backup script using Disk2VHD. I would like to change it a little bit so it would check the C disk drive usage and compare it with F drive, so old images would be only removed if there is not enough free disk space on F.

Currently it removes old images when more than 4 is already created.

REM
REM A simple backup system using disk2vhd
REM
REM version 1.3, by J.E.B., 2011-02-22
REM
REM requires 'disk2vhd.exe' to be in the path
REM

setLocal EnableDelayedExpansion

REM "DRIVES" can be one drive identifier with colon, multiple separated by spaces,
REM or asterisk for all.  
REM "DEST" can be a drive letter or a UNC.

SET DRIVES="C:"
SET DEST="F:"

REM Keep most recent 4 VHD files in DEST, delete the rest

for /f "skip=4 tokens=* delims= " %%a in ('dir/b/o-d %DEST%\*.VHD') do (
del %DEST%\%%a
)

REM Backup to VHD

C:
cd \
DISK2VHD %DRIVES% %DEST%\%COMPUTERNAME%--%date:~-10,3%%date:~-7,2%%date:~-4,4%.VHD

EXIT /B n

Answer 1

Here it is - a working script!

# Null all the values
$Cdisk = $null
$Fdisk = $null
$CdiskCapacity =  $null
$CdiskFree =  $null
$CdiskUSed =  $null

#This function is called to determine the used space on the C: drive
function UsedDiskSpace() {
$Cdisk = Get-WmiObject Win32_LogicalDisk -Filter "DeviceID='C:'" | Select-Object Size,FreeSpace
$CdiskCapacity = $Cdisk.size/1073741824
$CdiskFree = $Cdisk.freespace/1073741824
$CdiskUSed = $CdiskCapacity-$CDiskFree
return $cdiskUsed
}

#This function is called repeatedly until the space on the F: drive is greater than the used space on the C: drive
function FreeDiskSpace() {
$Fdisk = Get-WmiObject Win32_LogicalDisk -Filter "DeviceID='F:'" | Select-Object Size,FreeSpace
$Fdisk = $Fdisk.freespace/1073741824
return $Fdisk
}

#This function will simply delete the oldest file in the root of the F: drive
Function DelVHD {
Get-ChildItem F:\ | Sort CreationTime | Select -First 1 | Remove-Item -force -Recurse
}

#Create the VHD - pass $true to run the Disk2VHD program hidden; $False for visible. First run should be false to allow agreement of EULA.!
Function CreateVHD($Hidden) {
$filename = (get-date -uformat %d%b%y) + "_"  + $Env:COMPUTERNAME + ".vhd"
$filename = "F:\"+$Filename
    If ($Hidden -eq $True){
        start-process -WindowStyle Hidden c:\disk2vhd.exe -argumentlist 'c:', $filename # The .\ assumes disk2vhd is in the same folder as this script;
    }
        ElseIf ($Hidden -eq $False){c:\disk2vhd.exe c: $filename # The .\ assumes disk2vhd is in the same folder as this script;
    }
}

#This loop kicks everything off - it gets the free disk space, deletes files one at a time on F: as required and then creates the VHD when there is sufficient disk space freed up.
Do {
$c = useddiskspace
$f = freediskspace


if ($f -lt $c) {

write-host "Space used on C: = "$c
write-host "Free space on F: = "$f
write-host "Not enough free space on F: Drive. Deleting oldest image"
DelVHD
}
}
until ($f -gt $c)

write-host "Enough free space on F:\ found...creating latest VHD"
CreateVHD $true #NOTE - Run with $False so the Disk2VHD window is visible at least the first time in order to accept the EULA