none
Question on Quorum

    Question

  • Hi Experts,

    Couple of questions on Windows Clusters. I am not a cluster expert and look for some help to understand the concepts

    1. In Win 2003 cluster, we have quorum disk and "Disk only quorum model". IF this quorum model is used, and if quorum disk is down, then cluster is down.   So, my question is what quorum disk contain?  All I know is, it contains cluster related information. But what kind of info is stored in quorum disk which is so critical.

    2. Secondly, from Win 2008 and above cluster, we have new quorum models(i.e node majority, node + disk witness ...), in these new quorum models, do we still have quorum disk? And where does cluster information is stored? I came to know that cluster information is stored or replicated to all nodes and each node has its own copy.  I wanted to know is this true or not. pl correct me if am wrong. If this information is correct, how does the cluster info replication happens? Can anybody explain in simple terms?

    Any links/msdn blogs or resources would be a great help for reference.

    Thanks in advance.

          
    Monday, October 13, 2014 9:06 PM

Answers

  • This is like debating cassette players vs. VHS...

    While interesting, they are outdated technologies that really aren't that relevant anymore.  How things work in Win2012 R2 are completely different... so it's really not worth your time to learn the already outdated concepts.  I recommend focusing on Win2012 R2.

    Here's a presentation from TechEd that covers quorum discussion points... I hope it is helpful
    http://channel9.msdn.com/Events/TechEd/Europe/2013/MDC-B403#fbid=

    Thanks!
    Elden

    Tuesday, October 14, 2014 2:53 AM
    Owner
  • 2008 and later have changed to a witness disk.  It is not as critical as it was in 2003, but it is still important.  It does have a quorum vote and it does contain cluster configuration information.  But it can be lost and the rest of the cluster will continue to operate.  In 2012 it actually becomes dynamic.  If the cluster has an even number of host nodes, the witness disk is added to provide a quorum vote.  If there are an odd number of host nodes, the witness drops out because there is a quorum capability with the odd number of nodes.  This enables a cluster to lose multiple hosts and still continue operating as the quorum of the cluster changes dynamically as the available quorum is increased or decreased.

    . : | : . : | : . tim

    Monday, October 13, 2014 10:57 PM
  • The info stored on witness disk is not really critical, what is critical is node's access to the witness which can give the node an additional vote.

    2012 server still uses quorum modes that were introduced in 2008 server, but includes a number of improvements. Quorum settings GUI  includes an option to choose "default" quorum configuration, which lets the cluster to auto-configure quorum based on number of nodes and avilability of witness disk.

    A new "Dynamic Quorum" feature can now dynamically adjust number of node's and witness' votes in response to node failures, keeping total number of votes at odd number.

    Running cluster configuration is stored under \xx.cluster key in registry. If a disk witness is present, configuration data is also written to the witness disk.

    For more info see

    What's New in Failover Clustering in Windows Server

    Configure and Manage the Quorum in a Windows Server 2012 Failover Cluster


    Gleb.


    • Edited by Gleb F.NG Tuesday, October 14, 2014 12:02 PM
    • Marked as answer by Alex LvModerator Tuesday, October 28, 2014 9:27 AM
    Tuesday, October 14, 2014 8:00 AM
  • Hi Samantha v,

    For 2003 cluster before giving an explanation of what a cluster quorum is, it is important to understand the background to Windows Clustering Technologies.

    Starting with Microsoft® Windows NT® 4.0 Enterprise Edition, Microsoft introduced the idea of a cluster, which is simply a group of servers that are presented as one virtual server. For example, you can configure two servers, server A and server B, in a cluster, and present them to the outside world as server C (a virtual server). If, for example, server A dies, server B is used to ensure that the virtual server (server C) and the services it offered, are still available to clients, thereby providing transparent access to the user. You can refer the following related KB for more detail information:

    Background (Server Clusters: Quorum Options - Windows Server 2003)

    http://technet.microsoft.com/en-us/library/cc780689(v=ws.10).aspx

    Quorum Drive Configuration Information

    http://support.microsoft.com/kb/280345

    Frequently Asked Questions (Server Clusters: Quorum Options - Windows Server 2003)

    http://technet.microsoft.com/en-us/library/cc737067(v=ws.10).aspx

    For 2008 or later cluster you can refer the following article:

    New Cluster Quorum Models in Windows 2008

    http://blogs.msdn.com/b/saponsqlserver/archive/2010/06/30/new-cluster-quorum-models-in-windows-2008.aspx

    I’m glad to be of help to you!


    We are trying to better understand customer views on social support experience, so your participation in this interview project would be greatly appreciated if you have time.
    Thanks for helping make community forums a great place.

    Wednesday, October 15, 2014 7:05 AM
    Moderator

All replies

  • 2008 and later have changed to a witness disk.  It is not as critical as it was in 2003, but it is still important.  It does have a quorum vote and it does contain cluster configuration information.  But it can be lost and the rest of the cluster will continue to operate.  In 2012 it actually becomes dynamic.  If the cluster has an even number of host nodes, the witness disk is added to provide a quorum vote.  If there are an odd number of host nodes, the witness drops out because there is a quorum capability with the odd number of nodes.  This enables a cluster to lose multiple hosts and still continue operating as the quorum of the cluster changes dynamically as the available quorum is increased or decreased.

    . : | : . : | : . tim

    Monday, October 13, 2014 10:57 PM
  • This is like debating cassette players vs. VHS...

    While interesting, they are outdated technologies that really aren't that relevant anymore.  How things work in Win2012 R2 are completely different... so it's really not worth your time to learn the already outdated concepts.  I recommend focusing on Win2012 R2.

    Here's a presentation from TechEd that covers quorum discussion points... I hope it is helpful
    http://channel9.msdn.com/Events/TechEd/Europe/2013/MDC-B403#fbid=

    Thanks!
    Elden

    Tuesday, October 14, 2014 2:53 AM
    Owner
  • The info stored on witness disk is not really critical, what is critical is node's access to the witness which can give the node an additional vote.

    2012 server still uses quorum modes that were introduced in 2008 server, but includes a number of improvements. Quorum settings GUI  includes an option to choose "default" quorum configuration, which lets the cluster to auto-configure quorum based on number of nodes and avilability of witness disk.

    A new "Dynamic Quorum" feature can now dynamically adjust number of node's and witness' votes in response to node failures, keeping total number of votes at odd number.

    Running cluster configuration is stored under \xx.cluster key in registry. If a disk witness is present, configuration data is also written to the witness disk.

    For more info see

    What's New in Failover Clustering in Windows Server

    Configure and Manage the Quorum in a Windows Server 2012 Failover Cluster


    Gleb.


    • Edited by Gleb F.NG Tuesday, October 14, 2014 12:02 PM
    • Marked as answer by Alex LvModerator Tuesday, October 28, 2014 9:27 AM
    Tuesday, October 14, 2014 8:00 AM
  • Thank you very much for your guidance.

    @Elden Christensen, I completely agree with you that we need to start focusing on new features but we need to know the way the quorum works in the old days so that we can have better comparison and better understanding and if someone asks the difference, should be able in a position to explain it in a better way!

    Appreciate all for the help.

    Tuesday, October 14, 2014 11:04 AM
  • Hi Samantha v,

    For 2003 cluster before giving an explanation of what a cluster quorum is, it is important to understand the background to Windows Clustering Technologies.

    Starting with Microsoft® Windows NT® 4.0 Enterprise Edition, Microsoft introduced the idea of a cluster, which is simply a group of servers that are presented as one virtual server. For example, you can configure two servers, server A and server B, in a cluster, and present them to the outside world as server C (a virtual server). If, for example, server A dies, server B is used to ensure that the virtual server (server C) and the services it offered, are still available to clients, thereby providing transparent access to the user. You can refer the following related KB for more detail information:

    Background (Server Clusters: Quorum Options - Windows Server 2003)

    http://technet.microsoft.com/en-us/library/cc780689(v=ws.10).aspx

    Quorum Drive Configuration Information

    http://support.microsoft.com/kb/280345

    Frequently Asked Questions (Server Clusters: Quorum Options - Windows Server 2003)

    http://technet.microsoft.com/en-us/library/cc737067(v=ws.10).aspx

    For 2008 or later cluster you can refer the following article:

    New Cluster Quorum Models in Windows 2008

    http://blogs.msdn.com/b/saponsqlserver/archive/2010/06/30/new-cluster-quorum-models-in-windows-2008.aspx

    I’m glad to be of help to you!


    We are trying to better understand customer views on social support experience, so your participation in this interview project would be greatly appreciated if you have time.
    Thanks for helping make community forums a great place.

    Wednesday, October 15, 2014 7:05 AM
    Moderator