3 Replies Latest reply: Dec 19, 2012 2:09 AM by 632301 RSS

    Odd Number of Voting Disks

    632301
      Hi

      We are working on Oracle 11.2g two node RAC . At the time of clusterware installation we choose normal redundancy disk group for OCR.
      Afetr installation we check there are 3 vote disks with three failure groups.Is all voting disks contains some information and all nodes send heart to one voting disk.


      Please explain "why odd number of voting disk" .
        • 1. Re: Odd Number of Voting Disks
          Mahir M. Quluzade
          Hi,

          As you know, normal redundancy diskgroup for OCR and VOTE disks require 3 way mirror. HIGH redundancy require 5 way redundancy.

          Best practice needed to have an odd number of voting disks to ensure that a tie-breaking disk exists when the interconnect between nodes fails

          Odd numbers of Voting Disks are recommended because losing 1/2 or more of all of your voting disks will cause nodes to get evicted from the cluster, or nodes to evict themselves out of the cluster.

          You must have an odd number of voting files because you must guarantee that
          an intersect remains in the voting files that each node is accessing when access to
          one file is lost. If you have only two files and a node loses access to it, you cannot
          guarantee which file the other node can access, if any. If you have three voting files
          and lose access to one, you know that even if the other node loses access to one,
          both nodes will be accessing at least one common file. So with three voting files,
          you can tolerate loss of access to one file, but a loss of access to two files will mean
          a cluster reconfiguration has to happen

          Please check : Always ODD number of Voting disks.

          Regards
          Mahir M. Quluzade
          • 2. Re: Odd Number of Voting Disks
            632301
            Thanks a lot for relpy.

            As i mention we are using 2 node rac and for vote disks normal redundency diskgroup.that means only one voting disk but with 3 copies is it right.

            Another thing is the with 1 voting disks and 2 node rac if interconnect between node1 and node2 are fails and both the nodes are able to connect vote disk then what happen.

            Thanks in advance.
            • 3. Re: Odd Number of Voting Disks
              632301
              hi all

              please help me to understand "why odd number of vote disks" so that we we will move to add another 2 vote disks.

              Thanks