Balancing LUN Paths on your ESX Hosts with PowerShell

After watching this video that was posted by the VI Toolkit team, I immediately thought of this script that was posted quite a while back on Yellow Bricks. I decided to try to recreate this script in PowerShell, and while I was at it expand it so it would modify all nodes in a cluster at once. As such I wrote the following script. Please feel free to give feedback or make modifications! You can download it from my Sky Drive or check it out below:

# Cluster-wide LUN Path Load Balancing Script
# Written by Justin Emerson, http://vmjunkie.wordpress.com
# Idea originally from a PERL script I saw here:
#    http://www.yellow-bricks.com/2008/04/01/load-balancing-activeactive-sans/
# This script requires the VI Toolkit version 1.5
# NOTE: This script assumes that every LUN has the same number of paths.
#       If you have multiple storage arrays, and they have different numbers of paths,
#		I make no guarentees that this will work!
# If you have an improvement to this script, please feel free to leave a comment on my blog!
Write-Host "This script will modify the policy of all your shared LUNs on all ESX Servers" -ForegroundColor Cyan
Write-Host "in a Cluster to Fixed and select a preferred path in a round-robin fashion." -ForegroundColor Cyan
if ($args.Length -eq 0) {$clusterName = Read-Host "Please enter the Cluster name"} else {$clusterName = $args[0]}
$VMHosts = Get-Cluster $clusterName | Get-VMHost
# Run through this loop for each host in the cluster
foreach ($VMHost in $VMHosts)
{
	# Keep only disks of luntype "disk" to avoid any storageArrayController devices.
	# Filter to only objects where the ConsoleDeviceName starts with vml to avoid any DAS disks.
	# Note: I have tested both HP EVA and Xiotech storage and SAN LUNs always appear this way.
	# Please check if this is the same on your storage before running.
	$luns = $VMHost|get-scsilun -luntype disk|
	where-object {$_.ConsoleDeviceName -like "/vmfs/devices/disks/vml*"}|Sort-Object CanonicalName
	$firstLUNPaths = Get-ScsiLunPath $luns[0]
	$numPaths = $firstLUNPaths.Length
	$count = 0
	foreach ($lun in $luns)
	{
		if ($count -ge $numPaths) { $count = 0 }
		$paths = Get-ScsiLunPath -ScsiLun $lun
		$lun|Set-ScsiLun -MultipathPolicy Fixed -PreferredPath $paths[$count]
		$count += 1
		# Sleep for 30 seconds as I've heard some arrays dont like doing this too fast.
		Start-Sleep -Seconds 30
	}
}

Note that after running the script, my ESX servers had esxcfg-mpath -l an output of:

[root@tb20 root]# esxcfg-mpath -l
Disk vmhba1:0:3 /dev/sdc (307200MB) has 4 paths and policy of Fixed
 FC 14:0.0 500110a00016013e<->50001fe1500ef599 vmhba1:0:3 On
 FC 14:0.0 500110a00016013e<->50001fe1500ef59d vmhba1:1:3 On
 FC 23:0.0 500110a000160152<->50001fe1500ef598 vmhba2:0:3 On active preferred
 FC 23:0.0 500110a000160152<->50001fe1500ef59c vmhba2:1:3 On

Disk vmhba1:0:4 /dev/sdd (1048576MB) has 4 paths and policy of Fixed
 FC 14:0.0 500110a00016013e<->50001fe1500ef599 vmhba1:0:4 On
 FC 14:0.0 500110a00016013e<->50001fe1500ef59d vmhba1:1:4 On
 FC 23:0.0 500110a000160152<->50001fe1500ef598 vmhba2:0:4 On
 FC 23:0.0 500110a000160152<->50001fe1500ef59c vmhba2:1:4 On active preferred

Disk vmhba1:0:6 /dev/sdf (358400MB) has 4 paths and policy of Fixed
 FC 14:0.0 500110a00016013e<->50001fe1500ef599 vmhba1:0:6 On
 FC 14:0.0 500110a00016013e<->50001fe1500ef59d vmhba1:1:6 On active preferred
 FC 23:0.0 500110a000160152<->50001fe1500ef598 vmhba2:0:6 On
 FC 23:0.0 500110a000160152<->50001fe1500ef59c vmhba2:1:6 On

Disk vmhba1:0:1 /dev/sda (204800MB) has 4 paths and policy of Fixed
 FC 14:0.0 500110a00016013e<->50001fe1500ef599 vmhba1:0:1 On active preferred
 FC 14:0.0 500110a00016013e<->50001fe1500ef59d vmhba1:1:1 On
 FC 23:0.0 500110a000160152<->50001fe1500ef598 vmhba2:0:1 On
 FC 23:0.0 500110a000160152<->50001fe1500ef59c vmhba2:1:1 On

Disk vmhba0:0:0 /dev/cciss/c0d0 (139979MB) has 1 paths and policy of Fixed
 Local 6:0.0 vmhba0:0:0 On active preferred

Disk vmhba1:0:2 /dev/sdb (153600MB) has 4 paths and policy of Fixed
 FC 14:0.0 500110a00016013e<->50001fe1500ef599 vmhba1:0:2 On
 FC 14:0.0 500110a00016013e<->50001fe1500ef59d vmhba1:1:2 On active preferred
 FC 23:0.0 500110a000160152<->50001fe1500ef598 vmhba2:0:2 On
 FC 23:0.0 500110a000160152<->50001fe1500ef59c vmhba2:1:2 On

Disk vmhba1:0:5 /dev/sde (307200MB) has 4 paths and policy of Fixed
 FC 14:0.0 500110a00016013e<->50001fe1500ef599 vmhba1:0:5 On active preferred
 FC 14:0.0 500110a00016013e<->50001fe1500ef59d vmhba1:1:5 On
 FC 23:0.0 500110a000160152<->50001fe1500ef598 vmhba2:0:5 On
 FC 23:0.0 500110a000160152<->50001fe1500ef59c vmhba2:1:5 On

Disk vmhba1:0:7 /dev/sdg (102400MB) has 4 paths and policy of Fixed
 FC 14:0.0 500110a00016013e<->50001fe1500ef599 vmhba1:0:7 On
 FC 14:0.0 500110a00016013e<->50001fe1500ef59d vmhba1:1:7 On
 FC 23:0.0 500110a000160152<->50001fe1500ef598 vmhba2:0:7 On active preferred
 FC 23:0.0 500110a000160152<->50001fe1500ef59c vmhba2:1:7 On

Disk vmhba1:0:8 /dev/sdh (102400MB) has 4 paths and policy of Fixed
 FC 14:0.0 500110a00016013e<->50001fe1500ef599 vmhba1:0:8 On
 FC 14:0.0 500110a00016013e<->50001fe1500ef59d vmhba1:1:8 On
 FC 23:0.0 500110a000160152<->50001fe1500ef598 vmhba2:0:8 On
 FC 23:0.0 500110a000160152<->50001fe1500ef59c vmhba2:1:8 On active preferred

RAID Controller (SCSI-3) vmhba1:1:0  (0MB) has 4 paths and policy of Fixed
 FC 14:0.0 500110a00016013e<->50001fe1500ef59d vmhba1:1:0 On active preferred
 FC 14:0.0 500110a00016013e<->50001fe1500ef599 vmhba1:0:0 On
 FC 23:0.0 500110a000160152<->50001fe1500ef598 vmhba2:0:0 On
 FC 23:0.0 500110a000160152<->50001fe1500ef59c vmhba2:1:0 On

Yay, it worked!

---

Possibly related posts: (automatically generated)

• Configure Software iSCSI Multipathing to vSphere Datastores
• A Minor Landmark