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    SubjectRE: Production comparison between 2.4.27 and 2.6.8.1
    Date
    Nick Piggin wrote:

    > I wouldn't worry too much about hdparm measurements. If you
    > want to test the streaming throughput of the disk, run dd
    > if=big-file of=/dev/null or a large write+sync.

    Created a big file:
    -rw-r--r-- 1 root root 1073740800 Aug 22 17:22 /testfile

    time dd if=/testfile of=/dev/null gives:
    On 2.6.8.1 ext3 raid
    real 0m11.493s
    user 0m0.657s
    sys 0m2.796s
    On 2.6.8.1 xfs:
    real 0m18.214s
    user 0m0.697s
    sys 0m3.778s

    Tests on 2.6.8.1 has been done with elevator=deadline

    On 2.4.7 ext3 raid:
    real 0m20.513s
    user 0m0.704s
    sys 0m2.626s

    On 2.4.7 xfs:
    real 0m28.414s
    user 0m0.686s
    sys 0m3.320s

    So it seems that read access to disks is better on 2.6 tree.


    > Regarding your worse non-RAID XFS database results, try
    > booting 2.6 with elevator=deadline and test again.

    This are results obtained with deadline:

    filippo:~# dmesg |grep deadline
    Using deadline io scheduler

    A) [schema]
    2b) 2.6.8.1 and xfs
    real 0m0.551s
    user 0m0.027s
    sys 0m0.012s

    B) [Importing data]
    2b) 2.6.8.1 and xfs
    real 1m1.474s
    user 0m3.281s
    sys 0m1.505s

    It seems performance does not get better.

    I have tried other tests:
    With ext2 FS results are:



    A)
    1c) 2.4.7 and ext2 (no raid)
    real 0m0.625s
    user 0m0.028s
    sys 0m0.018s
    2c) 2.6.8.1 and ext2 (no raid)
    real 0m1.667s
    user 0m0.026s
    sys 0m0.010s
    B)
    1c) 2.4.7 and ext2 (no raid)
    real 1m28.542s
    user 0m3.232s
    sys 0m1.384s
    2c) 2.6.8.1 and ext2
    real 1m30.200s
    user 0m3.304s
    sys 0m1.461s

    Still, even with ext2, 2.4.7 performs much better with postgres (and
    likely other databases).

    I have no idea nor no clue how to improve this.

    > If yes,
    > are you using queueing (TCQ) on your disks?

    How can i check ?


    Massimo Cetra


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