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I've brought up a Windows Server 2008 box that has VMware Virtual Server on it. I have a 500 GB volume allocated from the SAN for the Datastore that will house the VM for a Windows Server 2008/SQL Server 2008 server. If it wasn't virtual, I would normally align this like: create partition primary align=64 assign letter=E format fs=ntfs unit=64K label="" nowait

This will be a test/dev box and I just want to see what the most common alignment would be.

Thanks

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4 Answers 4

up vote 3 down vote accepted

The alignment offset should be whatever is appropriate for the underlying storage and the requirements of the partitioning standard you are using. This applies no matter how many layers of abstraction are involved, you must ensure that each partition is aligned at it's own level (so the host NTFS volumes need to be aligned, and the Guest OS NTFS volumes need to be aligned even if they are physically presented from VMDK's sitting on an already aligned NTFS volume).

So for VMware Server running under W2K8 with a VMDK sitting on an NTFS partition. You should align the host partition and then align the volumes within the guest as well. If the volume you are concerned about is a RAW disk being presented to the Guest OS then you should just align that. The only thing you need to make sure of is that your offset is a multiple of the stripe size used on the underlying physical storage. If you use an unaligned volume within the guest then you will see IO's spanning stripe boundaries even if the underlying NTFS volume is aligned.

I'm pretty sure that Windows 2008 (and Windows 7) now automatically align volumes on a 1Meg boundary just to be sure that they are going to be safely aligned under almost all scenarios so I don't think you need to do anything specific for your case to ensure that it's all OK.

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If possible install ESXi (it is free as in beer) on the physical server and create the VMs inside ESXi. In ESXi (probably also in VMware Server) it is possible to assign a LUN to a VM. Advantage: less overhead; disadvantages: less flexibility and no load sharing. Do not forget to install VMware Tools, otherwise you will have very bad network and disk performance.

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Not possible in this situation. I'm working towards getting to ESXi but we aren't there yet as a department. –  jasoncrider Feb 11 '10 at 16:05

I found this link which at least gets me started. http://www.vmware.com/pdf/esx3_partition_align.pdf

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That is only appropriate for VMFS partitions via ESX however. –  Chopper3 Feb 11 '10 at 16:13
    
yea, but it's the first thing I found that even looked close to what I was looking for. –  jasoncrider Feb 11 '10 at 18:31
    
@Chopper - while that is only 100% relevant to ESX and VMFS datastores on block storage the principles (and reasons for them) apply to almost any logical storage stack that is ultimately delivered from physical volumes that are striped across multiple physical disks. –  Helvick Feb 11 '10 at 18:49

I need to clarify this first, it appears that you've got;

  • A bare-metal W2K8 box connected to a SAN of some type with a LUN exposed to it
  • VMWare Server running on the (I assume that's what you mean anyway, or do you mean something else?)
  • You want to create a VM on the NTFS volume you're creating on the LUN
  • You want to install another copy of W2K8 and MSSQL inside the VM and want the best performance.

Is that all correct?

If so then I would recommend that when you create the NTFS partition on the LUN that you use the 'create partition primary align=64' command as usual - this is the closest you'll come to being certain of optimal alignment.

If I'm wrong in my assumptions please clarify.

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Yep, that's all correct. –  jasoncrider Feb 11 '10 at 18:31

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