VMware Solutions Discussions

WinServer 2008, alignment, mbralign issue


If a Windows 2008 server is brought up fresh under VMWare, it is already aligned. There are two cases though where alignment of a server running WinServer 2008 may be necessary. The problem is when mbralign is used against a VM running Server 2008, the resulting VM will not start. I am not sure why this is the case. All of my Win2003 VMs have a single disk with one volume, the C: drive. All of my Win2008 VMs have a single disk that contains two volumes, a small 100MB System Reserved volume and the C: drive. I am not sure if this System Reserved volume is the reason that mbralign cannot be used.


I believe a VM running Win2003 can be upgraded to Win2008 as long as it is going from 32 to 32 bit or from 64 to 64 bit. If the original server is not aligned the resulting Win2008 VM will also be mis-aligned. In this case we would want to run mbralign to align it but as I mentioned above I cannot get Mbralign to work against Server 2008.


A physical server running Win2008 is brought into ESX with a P2V operation using VMWare converter. The resulting VM will not be aligned. In this case we would want to run mbralign to align it and cannot

Any thoughts?



MBRAlign does not support Windows Server 2008.  I filed a request for this support but I don't think that it will ever be on the roadmap.

Condition 1 is valid and there really isn't a method to resolve this other than a new VM and migrating data.

Condition 2 will not result in a mis-aligned VM if it was a fresh install of Win2008.


Any updates on this.  I have a bunch of windows 2008 servers that were built unaligned.  I really don't want to rebuild all of them.


I heard a new version of VSC is going to be released and it will have the ability to align VMs itself. Not sure if it will work on WinServer 2008


I didn't think that win 2k8 required alignment in physical or virtual environment as the offset was corrected in the os by Microsoft on win 7, win 2k8


If you run a Windows 2008 VM through VMware Converter 5.0, it should correct the alignment for you without having to rebuild the VM. Previous versions always mis-aligned VM's using either P2V or V2V.


As long as you are using MBR disks , you will have misaligned partitions.

Windows 2008 uses GPT partition layout by default so a clean install should result in an aligned VM but upgrading from a windows 2003 which uses MBR partition layout will cause misaligned I/O.

Also as the name says , its MBRalign and you should never use it for aligning a vmdk which has other partition layout such as GPT.


I somewhat disagree with your statement. You can use MBR disks as long as you follow these steps as described:

1. Launch "diskmgmt.msc" to auto-detect any new disks that you may have added.

2. Launch "diskpart" in an elevated command prompt window

3. Select the disk you want to partition

4. Then run the following command "create partition primary align=32"

5. Exit diskpart utility and close command prompt

6. In the "diskmgmt.msc" rescan the disks

7. Select the disk that you created the newly aligned partition in step #4

8. Right click on the partition and select format

9. Give the new volume a label

10. Select NTFS

11. For block type, select 4096k.

12. Select quick format

13. Click OK

14. Assign a drive letter i.e. 😧 or other available

If you follow these steps to a tee, your MBR partition will always be aligned even if you import it from a Windows 2003 server. As long as you follow the above steps, nothing says you cannot use MBR partitions in Windows 2003 and then later move them into a Windows 2008 OS.

If on the other hand, you are setting up a clean Windows 2003 Operating System, one way to ensure that you have an aligned OS partition is following these steps:

1. Boot using a WinPE Windows media CDROM

2. Launch diskpart

3. Select the disk you want to partition

4. Then run the following command "create partition primary align=32"

5. Assign a drive letter i.e. C:

6. Exit diskpart utility

7. Perform a quick format using the format command in dos prompt i.e. format C: /q /a 4096 /fs:ntfs

8. Reboot the system

9. Install Windows 2003 on the newly created partition without formatting it in the installer.