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Thin Client and Virtual Machines Thread, Multiple virtual discs in Technical; Is it possible, sensible (or what is 'best' practice) to connect two virtual discs to one virtual machine in Hyper-V? ...
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    Multiple virtual discs

    Is it possible, sensible (or what is 'best' practice) to connect two virtual discs to one virtual machine in Hyper-V? I was just about to begin setting up and began thinking about OS/data separation. How should this idealing work/be setup?

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    tmcd35's Avatar
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    Depends on what task the VM is being given. Certainly is possible and for things like File Servers this is exactly how I'd set it up - seperate VHD for OS and Data. That said most of my servers are single task so they just have a single VHD with the software loaded for that task. I tend to set the HDD size to the maximum supported, 127Gb I think, and use auto-expanding drives. Most of my images are around the 10-20Gb mark but can grow to the full 127Gb if ever needed thus doing away with the need for seperate hard drive images in most cases.

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    djones (24th May 2010)

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    This will be a file server. I was thinking about a fixed 50Gb VHD for the OS and another dynamic VHD for the DATA. Any thoughts?

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    danrhodes's Avatar
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    If the disk is going to be used for storing alot of files (FileServer) then it may be better to connect a physical drive using Raw Device Mappings to a SAN rather than using a VHD.

    D

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    djones (24th May 2010)

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    tmcd35's Avatar
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    Personally I'd say never used fixed disks without good reason. It'd come back and bite you eventually. But yes, I'd go for two dynamic drives, 1 for the OS and 1 for the file server DATA.

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    Just don't have (and won't have) a SAN. Would it be better to keep this as a physical box then rather than a VM?

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    danrhodes's Avatar
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    What virtualisation do you currenlty have in place? Do you plant to consolodate all your H/W onto Virtual Machines as if your only doing this 1 then it may be a fruitelss effort.

    If you already have virtualisation in place and don't currently have a SAN, or have any plans to purchase a SAN then Dynamic Disks are the way, as said above, it will come back and haunt you one day if you go with fixed disks.

    D
    Last edited by danrhodes; 24th May 2010 at 03:22 PM.

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    Yes. Only have one physical (2003 R2 - does everything) box at the moment and have just purchased another server. The plan is to create a new DC/File Server and transfer all files across from the existing one before demoting and wiping it. I'll then install Hyper-V on the old one and create a new virtual DC on that for backup. I'll also setup DFS at the same time to make moving files a little easier in the future. How does that sound?

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    danrhodes's Avatar
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    My only issue with that setup is the worry that the old server you plan to install Hyper-V on may not support Server 2008 or be able to handle any more than the one VM your are planning to install onto it?

    Why not set the new server as a Virtual Host, install Server 2008 and the Hyper-V role, do a Physical to Virtual Conversion of the exisitng DC and its disks and have it run on the new Server as a VM, this should be a fairly seamless process and can be done within a few hours with no noticable changes for the end users, then flatten the old server and have that running as a RODC in case of a temporary failure of your PDC?

    D
    Last edited by danrhodes; 24th May 2010 at 03:38 PM.

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    Quote Originally Posted by danrhodes View Post
    If the disk is going to be used for storing alot of files (FileServer) then it may be better to connect a physical drive using Raw Device Mappings to a SAN rather than using a VHD.

    D
    This would give best performance (just). However if in the future you intend to have a fail over cluster with a SAN for shared storage you can't do this - the passthrough (RAW) disk wouldn't be available if the VM failed over too another host.

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    Quote Originally Posted by danrhodes View Post
    My only issue with that setup is the worry that the old server you plan to install Hyper-V on may not support Server 2008 or be able to handle any more than the one VM your are planning to install onto it?
    Yes, still need to check the state of play with that one.

    Quote Originally Posted by danrhodes View Post
    Why not set the new server as a Virtual Host, install Server 2008 and the Hyper-V role, do a Physical to Virtual Conversion of the exisitng DC and its disks and have it run on the new Server as a VM, this should be a fairly seamless process and can be done within a few hours with no noticable changes for the end users, then flatten the old server and have that running as a RODC in case of a temporary failure of your PDC?
    ...that is fine but the existing DC is 2003 and I will eventually get rid of this completely. I did think of doing a P2V of it but I went against it as I decided it would be an additional step I didn't need if I just created a new virtual DC/File server, moved everything across and reloaded the old server again - hopefully as a virtual or physical 2008 DC.

    In your suggestion above, what would you then have running on the new server, a P2V of the existing plus a physical DC on that hardware or a virtual DC or nothing else?

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    On your new server I would run server 2008 and Hyper-V only. Then I would P2V your old DC onto the new server running Hyper-V then flatten the old and make it a physical backup DC.

    New Server (Hyper-V) ---> P2V of old DC
    ---> Other Virtual Servers

    Old Physical DC - Flatten and use as a Backup DC.

    D

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    Use fixed disks if you want the best performance, expanding disks are slower. See Checklist: Optimizing Performance on Hyper-V

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    Quote Originally Posted by teejay View Post
    Use fixed disks if you want the best performance, expanding disks are slower. See Checklist: Optimizing Performance on Hyper-V
    Passthrough disks – The passthrough disk feature allows the guest operating system to bypass the Hyper-V Host file system and access the disk directly. Disks that are made available to guest operating systems via passthrough must be set to “offline” in the Hyper-V host to ensure that both the host and guest operating system do not attempt to access the disk simultaneously. The passthrough disk does offer a marginal performance advantage over other disk storage options but does not support certain functionality of virtual disks, such as Virtual machine snapshots and clustering support. Therefore use of the passthrough disk feature is not recommended in a BizTalk or SQL Server environment because the marginal performance benefits are more than offset by the missing functionality.

    Still slightly better performance though but no good if you want to use clustering or SQL - Shame

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    I'll rephrase, use fixed size vhd's for performance over expanding vhds and yes for most performance use passthrough ;-)

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