Comments on: PowerCLI: Check Partition Alignment (Windows VMs Only)

By: Michael Ryom

Michael Ryom — Tue, 08 Feb 2011 09:35:15 +0000

Inspiret by your script I made one which takes the raid systems block size into account, and check if the disk is aligned to that… Fx windows 2008 has a disk offset of 1048576 which in the above scripts would show the disk as unaligned:

$vms = get-vm
$winvms = $vmsview | where {$_.Config.GuestId -match “win”}

Foreach($winvm in $winvms){$raidblocksize = 64; $wmivm = get-wmiobject -class “Win32_DiskPartition” -namespace “root\CIMV2″ -ComputerName $winvm.name; if($?){Foreach($obj in $wmivm){$a = $obj.StartingOffset/$obj.BlockSize/$raidblocksize; if($a % 2 -eq “0″){$a = “$True”}else{$a = “$false”}$winvm.name, $obj.Name, $a}}}

By: Wayne

Wayne — Wed, 10 Nov 2010 19:38:34 +0000

No, it should be divisible by 8192. See the $.01 best practices guide:
http://www.vmware.com/pdf/Perf_Best_Practices_vSphere4.0.pdf

“The alignment of your file system partitions can impact performance. VMware makes the following
recommendations for VMFS partitions:
* Like other disk-based file systems, VMFS suffers a penalty when the partition is unaligned. Using the
vSphere Client to create VMFS partitions avoids this problem since it automatically aligns the
partitions along the 64KB boundary.
* To manually align your VMFS partitions, check your storage vendor’s recommendations for the
partition starting block. If your storage vendor makes no specific recommendation, use a starting
block that is a multiple of 8KB.”

By: Daniel M (@dmVI)

Daniel M (@dmVI) — Wed, 02 Jun 2010 23:37:56 +0000

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

By: Alex Feigenson

Alex Feigenson — Tue, 04 May 2010 07:23:31 +0000

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!

By: PowerCLI - Windows VM Partition Alignment | Alex Feigenson's Blog

PowerCLI - Windows VM Partition Alignment | Alex Feigenson's Blog — Tue, 04 May 2010 07:23:10 +0000

[...] to keep my blog from becoming an wasteland, I bring you a modified version of a script I found here that enumerates virtual machines and then does a WMI call against each one to determine if the [...]

By: NotoriousBDG

NotoriousBDG — Mon, 25 Jan 2010 02:36:37 +0000

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”
}

By: Virtualization Short Take #34 - blog.scottlowe.org - The weblog of an IT pro specializing in virtualization, storage, and servers

Mon, 25 Jan 2010 00:03:14 +0000

[...] up is Arne Fokkema’s PowerCLI script to check Windows VM partition alignment. As one commenter pointed out, the fact that the starting offset isn’t 65536—which is [...]

By: Vincent

Vincent — Thu, 17 Dec 2009 14:58:17 +0000

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.

By: uberVU - social comments

uberVU - social comments — Wed, 16 Dec 2009 06:30:22 +0000

Social comments and analytics for this post…

This post was mentioned on Twitter by afokkema: New blog post: http://tinyurl.com/yd7syxx – PowerCLI: Check Partition Alignment (Windows VMs Only)…

By: Tweets die vermelden PowerCLI: Check Partition Alignment (Windows VMs Only) « ICT-Freak.nl -- Topsy.com

Tue, 15 Dec 2009 23:45:16 +0000

[...] Dit blogartikel was vermeld op Twitter door afokkema, vSphere PowerCLI. vSphere PowerCLI heeft gezegd: Partition alignment is important for max performance, here's a PowerCLI script that will check your Windows guests http://is.gd/5p8XK [...]