Estimating disk performance

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  • Estimating disk performance


    I'm trying to estimate how fast my disks can do on my dedicated mysql server. Which is currently doing average 140 qps and up to 300 qps at peak times.

    Using sysbench, I have prepared test data like:
    sysbench --test=fileio --max-time=60 --max-requests=1000000 --file-num=1 --file-extra-flags=direct --file-fsync-freq=0 --file-total-size=128M prepare
    And running benchmark:
    sysbench --test=fileio --max-time=60 --max-requests=1000000 --file-num=1 --file-extra-flags=direct --file-fsync-freq=0 --file-total-size=128M --file-test-mode=rndrd run

    After running benchmark 10 times I ended up with following numbers:
    82.46 Requests/sec executed/(1.2884Mb/sec)/approx. 95 percentile: 10.67ms
    166.38 Requests/sec executed/(2.5996Mb/sec)/approx. 95 percentile: 10.77ms
    146.69 Requests/sec executed/(2.2921Mb/sec)/approx. 95 percentile: 10.88ms
    139.84 Requests/sec executed/(2.185Mb/sec)/approx. 95 percentile: 10.87ms
    145.80 Requests/sec executed/(2.2781Mb/sec)/approx. 95 percentile: 10.83ms
    138.85 Requests/sec executed/(2.1696Mb/sec)/approx. 95 percentile: 10.86ms
    145.00 Requests/sec executed/(2.2657Mb/sec)/approx. 95 percentile: 10.83ms
    113.40 Requests/sec executed/(1.7718Mb/sec)/approx. 95 percentile: 10.85ms
    197.23 Requests/sec executed/(3.0817Mb/sec)/approx. 95 percentile: 10.44ms
    157.38 Requests/sec executed/(2.459Mb/sec)/approx. 95 percentile: 10.76ms

    average requests/sec is 143.3

    How do I know whether it's fast or not ?

    My setup: CentOS 5.2, 8Gb RAM, io scheduler is "noop"
    RAID1, Stripe Size: 64kB, 2 Seagate ST3500320NS disks technical spec http://www.seagate.com/ww/v/index.jsp?vgnextoid=8c045cf536b4 3110VgnVCM100000f5ee0a0aRCRD

  • #2
    Those are normal speeds for a 7200 rpm drive. If you're using RAID 1, you'll get redundency but no speed increase.

    Expect to get around 145 writing queries per second with that setup. If you need more speed, using a RAID 10 setup is usually the cheapest way to go.