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Different I/O performance each datafile same LUN

Hello guys

We have a strange case. We have a SAP , on Windows 2003, using SQL Server 2005, and using a EMC Clarion for Storage.

Globally , response time of SAP is very good.

SQL Server response time is good.

CPUs have an excellent performance


But we have noticed I/O performance of Datafiles of SQL server is not excellent. This database have 8 datafiles, and I/O per file, is between 10 and 20 ms. Is not bad, but is not excellent...

The curious thing is: the number of I/O is well balanced between 8 datafiles but ms/IO per each datafile is different, and is growing (!?). I mean:

MTPDATA1 Data I: 13,168392

MTPDATA2 Data I: 13,965697

MTPDATA3 Data I: 15,507416

MTPDATA4 Data I: 16,531073

MTPDATA5 Data I: 17,404987

MTPDATA6 Data I: 18,767620

MTPDATA7 Data I: 20,017096

MTPDATA8 Data I: 20,813471

Any explanation for this???

Thanks a lot for advance


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2 Answers

  • author's profile photo Former Member
    Former Member
    Posted on Jan 21, 2008 at 04:42 PM


    Check disk fragmentation of the data files.



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  • Posted on Jan 29, 2008 at 06:35 PM

    Hi guys

    I can confirm my theory.

    EMC Clarion Manager have performed changes on configurarion of SAN: one of them regarding to right alignment.

    Now, the disk access time have been improved, and now access time of each datafile is not sequentally but similars.

    In fact. there is a SAP Note very clarifier...886337

    Regards and thanks for your suggestions


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