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MPIO Reducing Throughput (MB/sec) RRS feed

  • Question

  • I am setting up the infrastructure for a Microsoft SQL Server 2008 R2 Data warehouse on Win Server 2008 R2 SP1.

    Server : HP DL 585 G7

    SAN: EMC VNX 5300

    2 HBA's dual port 8Gbps

    2 Brocade 5100 Swtiches

    All the links are 8Gbps. 4 zones are setup on each switch.

     

    Case 1: Only 1 Swtich

    When we had just a single switch connected(1 port from each HBA connected to switch1), then MPIO showed 4 paths . It was default configured with “Round Robin with Subset” policy. We could get a maximum throughput of 1270 MB/sec using SQLIO.

     Case 2: 2 Swtiches

     When the second switch was connected (1 port from each HBA connected to switch2) , MPIO identified 8 paths ( which is logically correct). Again the MPIO policy was same as before . However, the maximum throughput we get now using SQLIO is 780 MB/sec ( are we hitting the 8Gbps link bottleneck somewhere?).

     Questions

    1.       Any ideas on why more paths are decreasing the throughput?

    2.       Do we need to change the MPIO policy?

    3.       Is this caused by introducing a second switch ? ( i.e. connecting cables to the same Switch might have given us better than 1270 MB/sec)

    4.       Customer doesn’t have EMC PowerPath licenses. Is it required or native MPIO should suffice?

     

    Any inputs appreciated.

    Wednesday, October 19, 2011 7:11 AM