PowerCLI: Check Partition Alignment (Windows VMs Only)
December 15, 2009 8 Comments
Some time ago I already created a script to report the disk alignment status of your Windows VM’s. I updated the script so you are able to export it to a CSV or XML file.
$myCol = @() $vms = get-vm | where {$_.PowerState -eq "PoweredOn" -and ` $_.Guest.OSFullName -match "Microsoft Windows*" } | Sort Name foreach($vm in $vms){ $wmi = get-wmiobject -class "Win32_DiskPartition" ` -namespace "root\CIMV2" -ComputerName $vm foreach ($objItem in $wmi){ $Details = "" | Select-Object VMName, Partition, Status if ($objItem.StartingOffset -eq "65536"){ $Details.VMName = $objItem.SystemName $Details.Partition = $objItem.Name $Details.Status = "Partition aligned" } else{ $Details.VMName = $objItem.SystemName $Details.Partition = $objItem.Name $Details.Status = "Partition NOT aligned" } $myCol += $Details } } $myCol | Export-Csv -NoTypeInformation "C:\Temp\PartitionAlignment.csv" #$myCol | Export-Clixml "C:\Temp\PartitionAlignment.xml"
The script uses WMI to gather the information about the partition of the Windows VM. So if you’re using a Firewall, be sure to open the right ports. More info about WMI and Firewalls, can be found over here: http://msdn.microsoft.com/en-us/library/aa822854%28VS.85%29.aspx
The output will look like this:
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The fact that a partion doesn’t start at offset 65536 doesn’t mean it is not aligned. Windows 2008 leaves the fist megabyte of the disk unused. This is still an aligned situation although your script will say it’s not. To really make sure a disk is aligned use the instruction from the following article: http://msdn.microsoft.com/en-us/library/dd758814.aspx
In short: Issue the following command on the client:
wmic partition get BlockSize, StartingOffset, Name, Index
and then
fsutil fsinfo ntfsinfo c:
you can use any other drive letter ofcourse.
Divide the StartingOffset from the first command with the “Bytes Per Cluster” from the second command. If the outcome is a integer then the disk is aligned.
This should all be doable with scripting of course.
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The starting offset does not have to be 65536, but it should be divisible by 65536. If you change your if statement to use mod, it will be more accurate.
if (($Partition.StartingOffset % 65536) -eq 0) {
$Details.VMName = $objItem.SystemName
$Details.Partition = $objItem.Name
$Details.Status = “Partition aligned”
}
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Thanks for the script, I modified it slightly and posted it on my blog – just a quick elseif for another alignment size.
I spent a good awhile reading your whole site, and I learned a great deal about powercli – many thanks!
Do you know if the WMI call captures info for Dynamic Disks correctly? According to an MS Technet article, WMI calls done locally (using the wmic command) don’t return Dynamic Disk information “reliably.” Not sure if the WMI call done remotely (leveraging PowerCLI as per your article) is any different. As per the MS article:
Important: Neither the output of the wmic command listed earlier nor any other tool designed only for basic disks reliably reports starting partition offsets of Windows dynamic disks.
Article located at URL http://msdn.microsoft.com/en-us/library/dd758814.aspx