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HyperV, Failover Cluster and Cluster Shared Volume: where to create the VMs ? RRS feed

  • Question

  • Hello,

    So we have the following configuration:

    Hyper V running on Windows Server 2012 R2.

    Then we created a Failover Cluster and added 2 Cluster Shared Volume. Everything looks ok.

    My question:

    I can create a VM directly on the Hyper-V manager on one of the node, using the CSV disk as storage. I won't be seen on the Failover Cluster though.

    If I create multiple VMs on each local hyper-v nodes like that (so sharing same CSV, same LUN on SAN), how is the coordinator node going to be able to handle the metadata traffic and redirected i/o since none of the VMs appear in the Failover Cluster manager ?

    I mean can we use safely the CSV as storage for several VMs that are not part of the Failover Cluster ?

    I was thinking the Failover Cluster was mandatory in order to manage multiple VMs on the same LUN.

    Looking forward to your feedback.

    Thanks You

    CC

    Friday, December 11, 2015 12:59 AM

Answers

  • You can use Hyper-V manager to create "local" VMs on cluster node. Further, there is nothing that will prevent you from placing VM files on a CSV volume when you create VM using HV manager. This "local" VM will work just fine, but there will be no availability protection. I/O redirection functions at the file system level, so it will work for local VM just like for clustered one. To create a clustered VM, use Failover Cluster Manager.

    Gleb.

    • Proposed as answer by Leo Han Thursday, December 24, 2015 8:43 AM
    • Marked as answer by Leo Han Monday, December 28, 2015 7:46 AM
    Friday, December 11, 2015 8:21 AM
  • The cluster engineers have spent years making sure that clusters work reliably and efficiently.  What you are doing is bypassing all the things they have put in place, thereby ensuring that you are going to have problems.

    Rule number 1.  When you have clustered your Hyper-V hosts, use the Failover Cluster Management console to manage your VMs.  This ensures they are properly configured for failover and will perform as expected.  If something has to be done through the Hyper-V console, the cluster console will tell you that.

    Local VMs - yes, it is possible to create VMs on cluster nodes by using the Hyper-V console.  But you should this ONLY when you want to create the VMs using local storage.  NEVER create 'local' VMs on CSV storage.  It was not designed or tested for that scenario.

    I would highly recommend that you revisit what you are doing.  It is highly recommended to follow recommended practices as they are tried and proven.  You are forging into untested and untried territory.


    . : | : . : | : . tim

    • Proposed as answer by Leo Han Thursday, December 24, 2015 8:43 AM
    • Marked as answer by Leo Han Monday, December 28, 2015 7:46 AM
    Friday, December 11, 2015 2:40 PM

All replies

  • Hi CC,

    >>I can create a VM directly on the Hyper-V manager on one of the node, using the CSV disk as storage. I won't be seen on the Failover Cluster though.

    After VM is created on one node, open failover cluster manager. Right click on roles>configure role>select virtual machine. Then you could add the vm to cluster.

    >>If I create multiple VMs on each local hyper-v nodes like that (so sharing same CSV, same LUN on SAN), how is the coordinator node going to be able to handle the metadata traffic and redirected i/o since none of the VMs appear in the Failover Cluster manager ?

    If the VM is not added to cluster, the node is acting as a Hyper-V host. Failover cluster would not be in control of the vm.

    >>I mean can we use safely the CSV as storage for several VMs that are not part of the Failover Cluster ?

    As far as I know, yes.

    Best Regards,

    Leo


    Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Support, contact tnmff@microsoft.com.

    Friday, December 11, 2015 8:01 AM
  • You can use Hyper-V manager to create "local" VMs on cluster node. Further, there is nothing that will prevent you from placing VM files on a CSV volume when you create VM using HV manager. This "local" VM will work just fine, but there will be no availability protection. I/O redirection functions at the file system level, so it will work for local VM just like for clustered one. To create a clustered VM, use Failover Cluster Manager.

    Gleb.

    • Proposed as answer by Leo Han Thursday, December 24, 2015 8:43 AM
    • Marked as answer by Leo Han Monday, December 28, 2015 7:46 AM
    Friday, December 11, 2015 8:21 AM
  • I setup my cluster with without Failover, I basically use the cluster as a file server, so both servers can see the files on the san storage, then i simply created vms with the vms stored on that storage. works just fine but has no failover. I can also move vms from one Host to the other host, rather simply as the VHD's don't need to move because they both accessible from both servers within the cluster.

    Ahmed

    Friday, December 11, 2015 9:35 AM
  • Ahmed,

    Seems like a slightly odd way of doing it and could run you into some problems down the line although I guess in theory its ok. You would be best placed to add the VMs to the cluster (it takes seconds) as mentioned above and then specify the possible owners of the resource if you want them pinned to a specific host for a reason. I suspect that Microsoft would not support your configuration unless the VMs were clustered but I could be wrong!

    The co-ordination of the storage is still done by the cluster. The resource is just presented to both nodes in C:\ClusterStorage and that process of moving data / meta-data will remain the same providing the cluster is available. In a two node cluster, if you end up in a redirected state through loss of comms to a node then the chances are you're going to wish the VM configuration was clustered so it could just fire up on the other node anyway.

    Of note though - in 2012R2 you will be limited on what you can change in settings through Hyper-V manager as management should now be done through failover cluster manager and it will tell you that if you try and edit settings in Hyper-V manager.

    Tom

    Friday, December 11, 2015 10:51 AM
  • The cluster engineers have spent years making sure that clusters work reliably and efficiently.  What you are doing is bypassing all the things they have put in place, thereby ensuring that you are going to have problems.

    Rule number 1.  When you have clustered your Hyper-V hosts, use the Failover Cluster Management console to manage your VMs.  This ensures they are properly configured for failover and will perform as expected.  If something has to be done through the Hyper-V console, the cluster console will tell you that.

    Local VMs - yes, it is possible to create VMs on cluster nodes by using the Hyper-V console.  But you should this ONLY when you want to create the VMs using local storage.  NEVER create 'local' VMs on CSV storage.  It was not designed or tested for that scenario.

    I would highly recommend that you revisit what you are doing.  It is highly recommended to follow recommended practices as they are tried and proven.  You are forging into untested and untried territory.


    . : | : . : | : . tim

    • Proposed as answer by Leo Han Thursday, December 24, 2015 8:43 AM
    • Marked as answer by Leo Han Monday, December 28, 2015 7:46 AM
    Friday, December 11, 2015 2:40 PM
  • Hello,

    Thanks all for these valuable information. By any chance do you have any MS documentation about it I can rely on? I have a hard time finding white papers mentioning this specific scenario, providing details about what is recommended and what is not in that case.

    I mean something that would enforce what Tim was saying. I was kind of thinking the same way but I did not find any relevant doc stating that an implementation like the one Ahmed is describing is not supported and explaining why we should not do that.

    Thanks in advance

    CC

    Friday, December 11, 2015 5:11 PM
  • You are not likely to find white papers dealing with what is not supported - it is impossible to cover all the possible permutations.  What you can find is lots of information on recommended practices and how to configure clusters.  Simply search TechNet for 'cluster recommended practices' and you will find lots of information.

    . : | : . : | : . tim

    Friday, December 11, 2015 7:44 PM