SQL Server Performance

SQLIO - SAN - High Latency on... READS?

Discussion in 'Performance Tuning for Hardware Configurations' started by Keith Madaras, Aug 8, 2011.

  1. Keith Madaras New Member

    Hello all,

    There's a lot of back story here, yet I'll try an condense. We're running an OpenE SAN on a Dell 480 <-- think that's correct. OpenE didn't play nicely with the Perc 6i, so we replaced it with an LSI SAS 9265-8I with a GB of NV Cache, which it does seem to like much more and is natively supported in the SAN software.

    We're running a Hyper-V cluster with SQL 2000 as one of the guests, which is where we're having the issues. I'm running with 4 port MPIO to the SAN device and showing some great performance, yet where we're lacking is SQLIO, which reports high latency on READ functions (85% over 24ms), yet is well within the acceptable range for writes (exceeding the performance of the old physical box). For this I am ruling out the logical disk layout (RAID-50 in two sets striped across 8 disks).

    Write back is enabled on the card, adaptive read-ahead enabled, disk cache disabled. Latest firmware has been loaded as well.

    I haven't worked with the LSI cards much, more of an HP person, I'm used to being able to adjust the read/write cache allocation, yet LSI doesn't seem to present this option. Is it there yet hidden somewhere in the CLI?

    What I'm looking for is anything that I can try to get the read to match the write with this card, any input is appreciated.

    Thanks all,

  2. satya Moderator

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