locked
Setting up question RRS feed

  • Question

  • I built out a server with a mirrored data drive for which I intended to host  a clustered SQL and Exchange databases. However, I have found out that a virtual server uses exclusive access to the physical drive. Since I'm using the setup to learn about clustering and HyperV, I'd like to get some advice:

    1. Should I break the mirror and partition the drives for exclusive access for each virtual server?

    2. Can I mirror 2 virtual data drives?

    3. Would creating 4 mirrored partitions on two 2 TB drive work as as 4 physical disks that each can individually be taken off-line to connect to a virtual server?

    4. How would you configure the scenario?

    Thanks.


    Dan Slaby
    Sunday, March 27, 2011 7:22 PM

Answers

  • If you store your vhd files on a volume, consisting of 2 mirrored drives, the vhd files will be mirrored like any other file. It is recommended that you do not install anything on your host other than hyper-v, and therefor your data drives will only conatin vhd files.

    Exclusive access to a hard drive is when you choose not to store your VM's in vhd files, but to dedicate a drive using pass-through settings. In that case the drive will be offline and unusable on the hyper-v server. It's only used under special circumstances. The common setup is to use vhd files, because these can be expanded, copied and modified.

    Using a dedicated partition for each virtual machine was the way you built a failover cluster on windows server 2008, consisting of two or more hyper-v servers connected to a SAN. With server 2008 R2 you store all vhd files on CSV volumes (Clustered Shared Volume) for quicker migration and smoother cluster management. You can dedicate partitions locally on your Hyper-V server if you wan't. Doesn't matter really, but it will give you a nice structured server.

     

    You can install exchange and SQL servers as VM's, no problem, but there are cases where SQL servers are running heavy loads, and since it has it's hardware provisioned by a hypervisor and shared with other VM's, it will impact on performance in comparison to having direct access to the hardware.

     
    Since you're considering clustering, you shouldn't build a hyper-v, SQL and exchange cluster on the same machine. You should have at least 2 hyper-v servers connected to a SAN, and run clustered virtual machine instances of exchange and SQL. There are several how-to's, best practices and other guides on how to do this.


    Let me know if I can be of further assistance.
    • Marked as answer by dslaby Tuesday, March 29, 2011 4:01 AM
    Monday, March 28, 2011 6:42 PM

All replies

  • Hi!

    A hypervisor does not necessarily require exclusive access to a physical drive. A virtual machine will have it's hard drive stored in a .vhd file, and can be stored anywhere.

    It is recommended however not to store vhd files on your system drive. So if you have a mirrored data drive, you can store your virtual machines there.

    It is recommended not to run certain SQL servers in a virtual environment, due to performance issues.

    Monday, March 28, 2011 9:55 AM
  • I recall from Technet that a virtual machine vhd has exclusive access to a physical disk. What I'm asking is (1) if I create a data vhd and store it on a mirrored drive, does the mirror, mirror the data vhd? At this point I'm planning on breaking the mirror and creating 4 mirrored partitions. Will each partition allow me to attach each SQL vhd to one of the mirrored partitions? Can 2 data vhds be mirrored?

    What SQL servers have performance issues in a virtual environment? Is this an issue with memory conflict between SQL that can use up physical memory on a server? I've had some problems with SSIS in a virtual environment that required releasing memory in the virtual environment.


    Dan Slaby
    • Edited by dslaby Monday, March 28, 2011 6:01 PM expand question
    Monday, March 28, 2011 5:58 PM
  • If you store your vhd files on a volume, consisting of 2 mirrored drives, the vhd files will be mirrored like any other file. It is recommended that you do not install anything on your host other than hyper-v, and therefor your data drives will only conatin vhd files.

    Exclusive access to a hard drive is when you choose not to store your VM's in vhd files, but to dedicate a drive using pass-through settings. In that case the drive will be offline and unusable on the hyper-v server. It's only used under special circumstances. The common setup is to use vhd files, because these can be expanded, copied and modified.

    Using a dedicated partition for each virtual machine was the way you built a failover cluster on windows server 2008, consisting of two or more hyper-v servers connected to a SAN. With server 2008 R2 you store all vhd files on CSV volumes (Clustered Shared Volume) for quicker migration and smoother cluster management. You can dedicate partitions locally on your Hyper-V server if you wan't. Doesn't matter really, but it will give you a nice structured server.

     

    You can install exchange and SQL servers as VM's, no problem, but there are cases where SQL servers are running heavy loads, and since it has it's hardware provisioned by a hypervisor and shared with other VM's, it will impact on performance in comparison to having direct access to the hardware.

     
    Since you're considering clustering, you shouldn't build a hyper-v, SQL and exchange cluster on the same machine. You should have at least 2 hyper-v servers connected to a SAN, and run clustered virtual machine instances of exchange and SQL. There are several how-to's, best practices and other guides on how to do this.


    Let me know if I can be of further assistance.
    • Marked as answer by dslaby Tuesday, March 29, 2011 4:01 AM
    Monday, March 28, 2011 6:42 PM
  • A VHD is simply a file on a disk, it doesn't have exclusive access to it. If you are using a pass-through disk then the VM has exclusive access to that disk.

    If you want to get more info, not saying Mike isn't enough or is wrong, but the Hyper-V forum would be a better place to post for more info from more sources: http://social.technet.microsoft.com/forums/en-US/winserverhyperv/threads/

    You should also look at the related technet articles about what the requirements are for supported configurations of exchange:

    http://technet.microsoft.com/en-us/library/cc794548(EXCHG.80).aspx

    SQL "support": http://support.microsoft.com/kb/956893

     

    Monday, March 28, 2011 11:30 PM