Disk Alignment

Posted: March 11, 2009 in Celerra, Tips and Tricks, VMware

I wanted to post about something  I recently found made a significant difference in performance testing done on a Celerra NS20.

I found a  this post http://clariionblogs.blogspot.com/2008/02/disk-alignment.html at Clariion blog central which has an excellent explanation about how and why disk misalignment occurs, defiantly worth a read.

The NS20 I refer to above is our production Celerra we use for dedicated iSCSI storage with our 2 node HA/DRS cluster. So something I had to take into account was disk alignment at ESX/Celerra level as well as Virtual Machine disk alignment.

Looking through VMware documentation I was pleased to read, storage added through Virtual Center is automatically aligned so now I only had to worry about disk alignment for the virtual machines. Below is a step by step walk through of how to add a disk to a virtual machine and align at the 64k boundary.

Step1. Right Click on the Virtual Machine, Edit settings and highlight Hard Disk and select Next.

Step2. Select create a new virtual disk and select next.

Step3. Select a disk size and select to store the new disk with the virtual machine or use the specify a datastore option to place the new disk on a different datastore, select Next.

Step4. Leave the default options under advanced options and select next, and Finish to complete the hardware wizard.

Step5. Navigate to the console tab for the virtual machine and from the desktop right click on My Computer and select Manage, go to Disk Management.

Step6. Right click on Disk Management and select Rescan Disks.\

Step7. Now open a command prompt window and type the following commands.

Invoke Diskpart


Microsoft DiskPart version 5.2.3790.3959
Copyright (C) 1999-2001 Microsoft Corporation.
On computer: SQLDR

type the follow command to show disks

DISKPART> list disk

  Disk ###  Status      Size     Free     Dyn  Gpt
  ——–  ———-  ——-  ——-  —  —
  Disk 0    Online      8189 MB  8033 KB
  Disk 1    Online      8189 MB  8189 MB

You can see Disk 1 is the new disk we just added. Now select Disk 1.

DISKPART> select disk 1

Disk 1 is now the selected disk.

Now we create the partition and set it to the recommended alignment offset.

DISKPART> create partition primary align=64

DiskPart succeeded in creating the specified partition.

Now you can right click on the new volume and format with desired file system type.

Now if your using 2003 enterprise or datacener edition ive noticed a bug where you receive an error when trying to format, the only work around I could find was to assign a drive letter in disk part and then format. <strange>

DISKPART> assign letter=X

DiskPart successfully assigned the drive letter or mount point

 That’s it…. easy aye ! 



  1. Very nice job on this blog. Enjoying it alot haha.

    Subbed! 😛

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