1 2 Previous Next 18 Replies Latest reply: Oct 30, 2012 7:24 PM by 970981 Go to original post RSS
      • 15. Re: Write I/O performance to slow in RAC on ASM
        970981
        Thanks for all the suggestions guys. Today I am going to carve up a new test data space on the SAN to do the Orion and dd tests suggested.

        Levi, If I am reading the docs on ASM correctly, it will always use direct I/O and the file system options parameter does not apply to ASM only the disk_asynch_io paramter.

        Thanks,
        Chris
        • 16. Re: Write I/O performance to slow in RAC on ASM
          Levi Pereira
          Levi, If I am reading the docs on ASM correctly, it will always use direct I/O and the file system options parameter does not apply to ASM only the disk_asynch_io paramter.
          Yes, you are correct. I forgot this part. Only parameter disk_asynch_io count when using ASM.

          In the future (after solve this problem) use this note to determine if the I/O is acceptable.
          How to Tell if the IO of the Database is Slow [ID 1275596.1]
          • 17. Re: Write I/O performance to slow in RAC on ASM
            970981
            after running the dd tests, I was able to capture these results. the lowest throughput I see while writing to the SAN LUNS with dd is ~130 mb/s.
            Yet I still am only seeing about 10mb/s when issuing a CREATE TABLESPACE command. Today I will be doing ORION tests to see if there is any difference in those tests.

            Thanks,
            Chris

            [bin]# dd if=/dev/zero of=/san_dd_test/testfile bs=8192 count=500
            500+0 records in
            500+0 records out
            4096000 bytes (4.1 MB) copied, 0.00828276 s, 495 MB/s
            [bin]# dd if=/dev/zero of=/san_dd_test/testfile bs=8192 count=5000
            5000+0 records in
            5000+0 records out
            40960000 bytes (41 MB) copied, 0.101956 s, 402 MB/s
            [bin]# dd if=/dev/zero of=/san_dd_test/testfile bs=8192 count=50000
            50000+0 records in
            50000+0 records out
            409600000 bytes (410 MB) copied, 1.53434 s, 267 MB/s
            [bin]# dd if=/dev/zero of=/san_dd_test/testfile bs=8192 count=500000
            500000+0 records in
            500000+0 records out
            4096000000 bytes (4.1 GB) copied, 31.2667 s, 131 MB/s
            [bin]# dd if=/dev/zero of=/san_dd_test/testfile bs=8192 count=5000000
            5000000+0 records in
            5000000+0 records out
            40960000000 bytes (41 GB) copied, 301.046 s, 136 MB/s
            • 18. Re: Write I/O performance to slow in RAC on ASM
              970981
              So after a bunch of testing, I think we have nailed this issue down to latency in the I/O subsystem. I believe that the network was not properly setup to isolate the private interconnect traffic from the SAN traffic. Today we moved the SAN traffic of the 10gb network and VLAN setup and put it on a 10gb Fibre channel setup. We instantly saw data transfer rates of 60-70mb/s sustained while creating a table space.

              Thanks everyone for the suggestions and test procedures!

              I am always happy to find new tools to put in the toolbox.

              Thanks,
              Chris
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