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Nov 16 2010

How to specify VMware View Disposable Disk Drive Letter

VMware View 4.5 introduced a disposable disk that can be configured on a per pool basis. The disposable disk is a separate disk for the GuestOS paging and system temporary files. VMware View Manager deletes the disposable files, including the whole VMDK, every time a linked clone is powered off. I have written more about Disposable disks in this article: VMware View 4.5 Storage Tiering explained.

The drive letter used by the disposable disk is automatically assigned by VMware View Manager using the next available (unused) drive letter. This behaviour cannot be changed and in some cases this drive letter could coincide with a network share that is mapped via user logon script or AD group policies. In this case you normally would have to re-architect your drive mappings, but in some cases this could be very trick if the application using the mapped drive is a long term established or legacy application.

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As today the only possible way to specify a driver letter is to change the pool setting manually in ADAM.

If you use ADSI Edit or ldp and browse to “DC=vdi,DC=vmware,DC=int” the objects relating to Desktop Pools will be in some of the entries in OU=Server Groups. Selected the CN= that contains the desktop pool you want to change and edit the attribute pae-SVIVmPersistentDiskSpec.

Remove the entry that contains DiskUsage=SystemDisposable and add a new entry. The new entry should be:

DiskSize=4096;DiskUsage=SystemDisposable;UserSparse=true;MountPoint=<driveletter>;

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Now you only need to recompose your desktop pool and the virtual machine’s disposable disk will be using the drive letter specified by you. I do believe VMware is working on a fix to allow administrators to select the drive letter to be assigned to disposable disks, just like we do today with Persistent disks (User Data Disk).

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  1. Andre Leibovici

    Just found out this issue and solution is also covered on KB 1030108

  2. Philip

    This is exactly what I was looking for, and came up first in Google results. Don’t like the answer though :) Hopefully will be more user friendly in a 5.0 release.

  3. Andre Leibovici

    @Philip
    Philip, I believe VMware is working on the feature set for View 5.0, but not for View 4.6.

  4. Nick

    There is a very minor typo in the solution (which is more detailled than the VMWare solution!).
    The typo is:
    “DiskSize=4096;DiskUsage=SystemDisposable;UserSparse=true;MountPoint=;

    Should be …UseSparse…, not …UserSparse..
    I only mention this in case someone copy-pastes to save typing!

  5. Troy

    A recompose isn’t enough to effect this change. The virtual desktop needs to be deleted and recreated per the KB article (1030108) you mentioned. http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1030108

    “To change the drive mapping, you need to modify entries within the ADAM database. The changes do not take place within the virtual machine until the virtual machine is deleted and recreated, as recompose operations are not designed to change the drive letters by design.”

    Doh…

  6. SamuraiJack

    So if a recompose is not supported to stick this change, is the only option to get it to stick to go into the pool, remove the VM’s and have the pool recreate them? no one actually specified a process that works.

  7. Sing

    in View 5.1.x, you can specify a drive letter for Disposable disk for your desktop pool.

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