Multi-process RoboCopy Powershell script

multi_robocopy.ps1

###
#
# This script runs robocopy jobs in parallel by increasing the number of outstanding i/o's to the copy process. Even though you can
# change the number of threads using the "/mt:#" parameter, your backups will run faster by adding two or more jobs to your
# original set. 
#
# To do this, you need to subdivide the work into directories. That is, each job will recurse the directory until completed.
# The ideal case is to have 100's of directories as the root of the backup. Simply change $src to get
# the list of folders to backup and the list is used to feed $ScriptBlock.
# 
# For maximum SMB throughput, do not exceed 8 concurrent Robocopy jobs with 20 threads. Any more will degrade
# the performance by causing disk thrashing looking up directory entries. Lower the number of threads to 8 if one
# or more of your volumes are encrypted.
#
# Parameters:
# $src Change this to a directory which has lots of subdirectories that can be processed in parallel 
# $dest Change this to where you want to backup your files to
# $max_jobs Change this to the number of parallel jobs to run ( <= 8 )
# $log Change this to the directory where you want to store the output of each robocopy job.
#
####
#
# This script will throttle the number of concurrent jobs based on $max_jobs
#
$max_jobs = 8
$tstart = get-date
#
# Set $src to a directory with lots of sub-directories
#
$src = "G:\folder_to_copy\"
#
# Set $dest to a local folder or share you want to back up the data to
#
$dest = "\\server_name\G$\folder_to_copy\"
#
# Set $log to a local folder to store logfiles
#
$log = "c:\temp\multi_robocopy_logs"
mkdir $log
$files = ls $src
$files | %{
$ScriptBlock = {
param($name, $src, $dest, $log)
$log += "\$name-$(get-date -f yyyy-MM-dd-mm-ss)_robocopy.log"
robocopy $src$name $dest$name /E /nfl /XO /np /mt:20 /ndl > $log
Write-Host $src$name " completed"
 }
$j = Get-Job -State "Running"
while ($j.count -ge $max_jobs) 
{
 Start-Sleep -Milliseconds 500
 $j = Get-Job -State "Running"
}
 Get-job -State "Completed" | Receive-job
 Remove-job -State "Completed"
Start-Job $ScriptBlock -ArgumentList $_,$src,$dest,$log
 }
#
# No more jobs to process. Wait for all of them to complete
#

While (Get-Job -State "Running") { Start-Sleep 2 }
Remove-Job -State "Completed" 
  Get-Job | Write-host

$tend = get-date

new-timespan -start $tstart -end $tend