5 Replies Latest reply: May 8, 2010 7:59 PM by damorgan RSS

    RAC interview questions

    721101
      Project:

      The installation is on "Oracle Enterprise Linux 5.2 x86_64" and Oracle RAC 10GR2 on IBM x3850 M2 Servers and IBM N-Series storage connected via
      redundant Fibre-channel switches. They want to use ASM for disk handling.

      Questions are:
      1. How many voting disks do we need per cluster (considering we have a redundant Fibre-channel connections)?

      2. How many OCR disks do we need and what is the recommended access (OCFS2 or RAW)?

      3. How do we calculate the bandwidth needed for the cluster interconnect? We currently have configured 2 x 1Gbit Ethernet ports for this.

      Any thoughts?
      Thanks
        • 1. Re: RAC interview questions
          Billy~Verreynne
          user8803475 wrote:
          Questions are:
          1. How many voting disks do we need per cluster (considering we have a redundant Fibre-channel connections)?
          Recommended? 2.

          Voting disks should be mirrored.

          2. How many OCR disks do we need and what is the recommended access (OCFS2 or RAW)?
          Recommended? 3.

          OCR disks should be multiplexed. And on RAW disks as ocfs2 introduces another s/w layer and increases CRS dependency and complexity.

          3. How do we calculate the bandwidth needed for the cluster interconnect? We currently have configured 2 x 1Gbit Ethernet ports for this.
          Not possible. You cannot accurately thumbsuck what loads will be put on the Interconnect. The Interconnect has two primary requirements - performance and scalability.

          And 1Gb ethernet ports are neither.
          Any thoughts?
          Well, seems like you are asking the very same questions under different guises here and on the RAC forum. And that I do not appreciate at all....

          Ask once. If you want more details, bump the thread, or phrase your questions differently. But asking these under different guises is not going to change the default answers.
          • 2. Re: RAC interview questions
            721101
            Sorry Billy
            I discovered that this DBA is somebody else that have the same interview questions, the questions is emailed , that is why we are typical :)

            sorry again , but this is really funny
            expect the same 3 exctly questions to be asked again from another DBA
            hehehhehehhehehhe
            • 3. Re: RAC interview questions
              436634
              see more Oracle RAC interview questions and answers at ..

              http://dbaregistry.blogspot.com/2010/02/oracle-rac-interview-questions.html
              • 4. Re: RAC interview questions
                561093
                Billy,

                Shouldn't it be the other way.
                1. How many voting disks do we need per cluster (considering we have a redundant Fibre-channel connections)?
                
                Recommended? 3.
                
                Voting disks should be multiplexed.
                
                2. How many OCR disks do we need and what is the recommended access (OCFS2 or RAW)?
                
                Recommended? 2.
                
                OCR should be mirrored.
                Asif Momen
                http://momendba.blogspot.com
                • 5. Re: RAC interview questions
                  damorgan
                  The critical thing with the cache interconnect is not bandwidth ... it is latency. Again GigE is not the best possible solution. But if the application is properly written and designed around node affinity and services it shouldn't be that big a deal though in the real-world it is.

                  What I find fascinating is that the single most important aspect of RAC I see done incorrectly in database after database including at some of Oracle's largest customers is the creation of services using DBMS_SERVICE. If someone does not understand the difference between CLB_GOAL_SHORT and CLB_GOAL_LONG I don't see how they can be successful.