4 Replies Latest reply on Sep 19, 2011 8:09 AM by user614534

    How to calculate network bandwidth for dataguard 11.2

    user614534
      Hi all,
      have a customer who needs to setup a new data guard environment in release 11.2.0.2. Primary site will be in Italy, standby site will be in New York.
      He would like to know the network bandwidth between primary and standby site needed to obtain the maximum performance in redo transport with or without compression option.
      I found a lot of threads and docs indicating some formulas but none of them explained how to:
      - calculate network bandwidth on a rac system (having a single instance standby database)
      - calculate network bandwidth in case of use redo transport compression
      - calculate cpu consumption if using redo transport compression

      Could you please give any advice?

      A.M.
        • 1. Re: How to calculate network bandwidth for dataguard 11.2
          692730
          We have always used the following to map out the avg log switches per hour. The query also shows the number of log switches per day.

          SELECT trunc(first_time) DAYS,
          count(*) NUM_SWITCHES,
          trunc(count(*)*log_size/1024/1024/1024) TOTAL_SIZE_IN_GB,
          to_char(count(*)/24,'9999.9') AVG_SWITCHES_AN_HOUR
          FROM v$loghist,
          (select avg(bytes) log_size from v$log) GROUP BY trunc(first_time),log_size order by DAYS

          Here is sample output:

          DAYS NUM_SWITCHES TOTAL_SIZE_IN_GB AVG_SWITCHES_AN_HOUR
          --------- ------------ ---------------- --------------------
          30-AUG-11 160 5000 6.7
          31-AUG-11 192 6000 8.0
          01-SEP-11 191 5968 8.0


          - Wilson
          www.michaelwilsondba.info
          • 2. Re: How to calculate network bandwidth for dataguard 11.2
            user614534
            Could you please take a look at
            http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/6006ac18-7900-2e10-a793-ee2d6b39063f?QuickLink=index&overridelayout=true

            This is specific for SAP but it contains other good suggestions to obtain information about redo log size per seconds. In this article you will find also the following formula:
            Required bandwidth = ((Redo generate bytes per sec. / 0.7) * 8) / 1,000,000 = bandwidth in Mbps
            My questions are:
            1) is this formula still good for 11.2?
            2) and if source database ia a 2 node rac?
            3) and if I use advanced compression option?
            • 3. Re: How to calculate network bandwidth for dataguard 11.2
              692730
              1) is this formula still good for 11.2?
              I'm sure this is still going to be accurate for 11.2. I don't see any reason why it would not be. When we do our calculations, it is all with/for database 11.2.0.2
              2) and if source database ia a 2 node rac?
              Does't matter if it is a 2 node or 4 node rac. The rac is still represented as 1 database.

              What is the standby going to be? rac or single node?
              3) and if I use advanced compression option?
              The data will not be sent compressed. It will be uncompressed data. Once received and applied on the standby...it will be compressed.

              - Wilson
              [www.michaelwilsondba.info|www.michaelwilsondba.info]
              • 4. Re: How to calculate network bandwidth for dataguard 11.2
                user614534
                Hi,
                customer made ma a lot of technical question just like the following:
                - which are the main factors determining the 30% overhead indicated in the network bandwidth calculation
                Required bandwidth = ((Redo rate bytes per sec. / 0.7) * 8) / 1,000,000 = bandwidth in Mbps
                - how much bandwidth will I gain if I apply redo transport compression and why redo transport compression and why usually the gzip utility gives me 5X less and oracle compression gives me a maximum of 50-60% of compression even if it uses the same engine of zlib compression as indicated below?
                -----------------------------------
                Data Guard redo transport compression uses the same zlib compression engine at level 1 as gzip -1. To estimate the compression ratio you can achieve using Data Guard redo transport compression, first compress an archived redo log file with gzip:

                $ gzip -1 <archive redo logfile>.arc

                Then use the gzip --list option to explicitly display the compression ratio:

                $ gzip --list <archive redo logfile.arc>.gz

                Note: Use gzip version 1.3.3 or later. Refer to www.gzip.org for the latest information on gzip.
                -------------------------------------

                Could anyone give me any direction?

                Thank you

                AM