Powershell backup script using Robocopy

backup.ps1

#requires -RunAsAdministrator

function Robocopy-Backup {
    <#
    .SYNOPSIS
        Backup a directory or multiple directories using robocopy
    .DESCRIPTION
        This script will backup a directory or multiple directories using robocopy. It will create log files per job in the specified log directory.
    .PARAMETER SourceDirectory
        The source directory to backup, e.g. 'G:\'. Can not be used with SourceDirectories or SourceDestinationPairs parameters.
    .PARAMETER SourceDirectories
        Multiple source directories to backup, e.g. 'G:\' and 'H:\'. Can not be used with SourceDirectory or SourceDestinationPairs parameters.
    .PARAMETER DestinationDirectory
        The destination directory to backup to, e.g. 'H:\'.
    .PARAMETER SourceDestinationPairs
        The source and destination directories to backup, e.g. @{src='G:\';dst='H:\'}, @{src='H:\';dst='I:\'}. Can not be used with SourceDirectory or SourceDirectories parameters.
    .PARAMETER LogDirectory
        The directory to store the logs in, defaults to 'C:\Logs\'.
    .EXAMPLE
        Robocopy-Backup -SourceDirectory "G:\" -DestinationDirectory "H:\" -LogDirectory "C:\Logs\"
    .EXAMPLE    
        Robocopy-Backup -SourceDirectories "G:\", "H:\" -DestinationDirectory "I:\" -LogDirectory "C:\Logs\"
    .EXAMPLE
        Robocopy-Backup -SourceDestinationPairs @{src='G:\';dst='H:\'}, @{src='H:\';dst='I:\'} -LogDirectory "C:\Logs\"
    #>
    [CmdletBinding(DefaultParameterSetName="SingleSource")]
    Param(
        [Parameter(Mandatory=$true, ParameterSetName="SingleSource", HelpMessage="The source directory to backup, e.g. 'G:\'")]
        [string]$SourceDirectory,
        
        [Parameter(Mandatory=$true, ParameterSetName="MultiSource", HelpMessage="Multiple source directories to backup, e.g. 'G:\' and 'H:\'")]
        [string[]]$SourceDirectories,

        [Parameter(Mandatory=$true, ParameterSetName="SingleSource", HelpMessage="The destination directory to backup to, e.g. 'H:\'")]
        [Parameter(Mandatory=$true, ParameterSetName="MultiSource", HelpMessage="The destination directory to backup to, e.g. 'H:\'")]
        [string]$DestinationDirectory,

        [Parameter(Mandatory=$true, ParameterSetName="MultiSourceAndDestinations", HelpMessage="The source and destination directories to backup, e.g. @{src='G:\';dst='H:\'}, @{src='H:\';dst='I:\'}")]
        [pscustomobject[]]$SourceDestinationPairs,
        
        [Parameter(Mandatory=$false, HelpMessage="The directory to store the logs in, defaults to 'C:\Logs\'")]
        [string]$LogDirectory = "C:\Logs\robocopy-backup\"
    )

    Begin {
        # Start a stopwatch to measure the time taken
        $sw = [System.Diagnostics.Stopwatch]::StartNew()

        # Set the location to the script root
        Set-Location -Path $PSScriptRoot

        Write-Host "Starting backup at $(get-date -f "yyyy/MM/dd hh:mm:ss")"

        $robocopy_block = {
            <#
            .SYNOPSIS
                Backup a directory using robocopy
            .DESCRIPTION
                This script will backup a directory using robocopy. It will create a log file in the specified log directory.
            .PARAMETER src
                The source directory to backup, e.g. 'G:\'.
            .PARAMETER dst
                The destination directory to backup to, e.g. 'H:\'.
            .PARAMETER log
                The log file to write to, e.g. 'C:\Logs\backup_yyyy-MM-dd_hh-mm-ss.log'.
            #>
            param(
                [Parameter(Mandatory=$true, HelpMessage="The source directory to backup, e.g. 'G:\'")]
                [string]$src,

                [Parameter(Mandatory=$true, HelpMessage="The destination directory to backup to, e.g. 'H:\'")]
                [string]$dst,

                [Parameter(Mandatory=$true, HelpMessage="The log file to write to, e.g. 'C:\Logs\backup_yyyy-MM-dd_hh-mm-ss.log'")]
                [string]$log
            )

            # Create log file
            New-Item -Force $log | Out-Null
            
            # Execute robocopy command
            robocopy $src $dst /MIR /ZB /MT /XJ /XD Temp /R:3 /LOG:$log /NP
                # /MIR          # mirroring the folders, removing non-existant files. We don't want lots of old files cluttering up the backup 
                                # and the File Shares should keep a history on their own
                # /ZB           # copies files such that if they are interrupted part-way, they can be restarted
                # /MT           # copies using multiple cores, good for many small files
                # /XJ           # Ignoring junctions, they can cause infinite loops when recursing through folders
                # /XD Temp      # Temp directories shouldn't have important data files
                # /R:3          # Retrying a file only 3 times, we don't want bad permissions or other dumb stuff to halt the entire backup
                # /LOG:$log     # Logging to a file internally, the best way to log with the /MT flag
                # /NP           # Removing percentages from the log, they don't format well

            # Remove hidden and system attributes from the destination directory
            attrib -h -s $($dst.TrimEnd("\"))

            "Backup directory is complete. [$src -> $dst] ($log)"
        }

        function Get-FormattedDateTime {
            return $(get-date -f yyyy-MM-dd_hh-mm-ss_fff)
        }

        function Get-JobName {
            return "backup_$(Get-FormattedDateTime)"
        }

        function Get-LogFileName {
            return Join-Path $LogDirectory "$(Get-JobName).log"
        }
    }

    Process {
        switch ($PSCmdlet.ParameterSetName) {
            'SingleSource' {
                Write-Host "Backing up $SourceDirectory -> $DestinationDirectory"
                $log = Get-LogFileName

                # Run the robocopy command
                Invoke-Command $robocopy_block -ArgumentList $SourceDirectory,$DestinationDirectory,$log | Out-Null
            }

            'MultiSource' {
                # Loop through each source directory
                foreach ($dir in $SourceDirectories) {
                    $src = $dir
                    $dst = $DestinationDirectory
                    $log = Get-LogFileName
    
                    Write-Host "Backing up $dir -> $dst"
    
                    # pass the loop variable across the job-context barrier
                    Start-Job $robocopy_block -ArgumentList $src,$dst,$log -Name $(Get-JobName) | Out-Null
                }
            }
            
            'MultiSourceAndDestinations' {
                # Loop through each source/destination directory pair
                foreach ($pair in $SourceDestinationPairs) {
                    $src = $pair.src
                    $dst = $pair.dst
                    $log = Get-LogFileName
    
                    Write-Host "Backing up $src -> $dst"
    
                    # pass the loop variable across the job-context barrier
                    Start-Job $robocopy_block -ArgumentList $src,$dst,$log -Name $(Get-JobName) | Out-Null
                }
            }
        }

        # Wait for all to complete
        While (Get-Job -State "Running") { 
            Start-Sleep 2 
        }
    }

    End {
        # Display output from all jobs
        Get-Job | Receive-Job

        # Cleanup
        Remove-Job *

        Write-Host "Backup complete at $(get-date -f "yyyy/MM/dd hh:mm:ss")"

        Write-Host "Processing took: " -NoNewline
        Write-Host -ForegroundColor Magenta "$("{0:hh}h:{0:mm}m:{0:ss}s" -f $sw.Elapsed)"
    }
}