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Snapshots, fast disks, and the best Disk Management strategy RRS feed

  • Question

  • Hi,

    I have a server running Server Core + Hyper-V. Everything is going quite well with the initial VM deployments - and now it's time to tune the disk use for 'long-term' use. One this server we have two fast striped 10K disk arrays, each of ~300G, and a larger but slower 1T array.

    Obviously I want the VMs that are running to be on the fast arrays. Using VMM I managed this by using the 1T disks as a library, and migrated the images I needed to run to one of the fast arrays.

    What is the Hyper-V equivalent? From reading I think the snapshot directories for each VM should point to the slower disk... and Hyper-V is clever enough to copy the 'current' snapshot to the fast disk for use. Is this correct? If not - what is the best disk architecture for using VMs and snapshots under Hyper-V.

    Thanks,

    Nicholas

    Tuesday, April 15, 2008 5:53 PM

All replies

  • Are you talking about VM Snapshots or VSS Snapshots?  For VM Snapshots you should configure them to be on your fast disk.  Ideally you should only use VSS snapshots for production systems.

     

    Cheers,

    Ben

     

    Friday, April 18, 2008 6:10 AM
  • Hi Ben,

    I’m talking about VM snapshots. My previous workflow was to store unused VMs in a library on the slower disks, and move a whole VM to one of the fast arrays for use. Given the limited VMM snapshot implementation (navigating to an earlier snapshot deleted all newer snapshots), it was easier just to create new machines to represent different test-lab scenarios, and use the snapshots in way similar to multiple ‘undo’ disks, kept only for the duration of the test.

     

    With the new Hyper-V snapshot implantation, I can create extensive dependant test environments (thank you, again!) between which I can navigate by ‘Applying’ my snapshot of choice. This changes the workflow in that I have many more snapshots for each VM… and am running out of space on the fast arrays!


    So, a better way to phrase my question is: I see three places where the user can choose locations to persist VM components

    1. The VM config files (.xml, etc.)

    2. The .vhd itself

    3. The location, per VM for the snapshots


    Can I place the base .vhd’s on the slower array without any loss of performance for the snapshots? I work almost exclusively with snapshots anyways. To explain my initial posting: I had misread somewhere that the internal architecture of the snapshots was such that they are stored in their own location – but that the ‘active’ image is copied to a ‘working’ location. Were this true, I’d like to store the snapshots on the slower drive too, and somehow have the working image on the fast drive.


    All thoughts and corrections welcome,

     

    Nicholas

    Friday, April 18, 2008 2:26 PM
  • The snapshot disks are used in any read operation (not in writes though) - so storing them on slow media will affect the performance of the virtual machine.

     

    Cheers,

    Ben

    Wednesday, May 7, 2008 6:52 PM