Primary Storage

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  • 1.  question about I/O capacity

    Posted Mon February 15, 2021 12:57 PM
    Hello all

    I have a question about the explanation of the performance impact of Flashcopy in an FS7200

    On https://www.ibm.com/support/knowledgecenter/sl/ST3FR7_8.3.1/com.ibm.fs7200_831.doc/svc_configbackendsefc_3xmwwx.html is stated:

    To calculate the average I/O rate per volume, use the following equation:
    I/O rate = (I/O capacity) / ( V + weighting factor for FlashCopy + weighting factor for volume mirroring + weighting factor for thin-provisioned)

    For example, consider 20 volumes with an I/O capacity of 5250, a FlashCopy weighting of 28,
    a mirroring weighting of 5, and a thin-provisioned weighting of 0.25. The I/O rate per volume is 5250 / (20 + 28 + 5 + 2.5) = 94.6.
    This estimate is an average I/O rate per volume; for example, half of the volumes might be running at 200 I/O operations per second (IOPs),
    and the other half might be running at 20 IOPs. However, this rate would not overload the system because the average load is 94.6.

    What do they mean in this context by I/O Capacity 5250? How to calculate this or find out?

    Thanks.

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    T Masteen
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  • 2.  RE: question about I/O capacity

    Community Leadership
    Posted Mon February 15, 2021 05:45 PM

    @BYRON GROSSNICKLE​ can you answer this one?

    @Maria Altamirano Borrego @JORGE ENRIQUE ESCALANTE RAMONET any ideas?
    ​​​

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    Peter Basmajian
    Worldwide Product Marketing and Advocacy, IBM
    San Francisco CA 720-396-5694
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  • 3.  RE: question about I/O capacity

    Posted Tue February 16, 2021 11:26 AM
    I am trying to get in touch with development and find an answer to the question.  Thanks.

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    BYRON GROSSNICKLE
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  • 4.  RE: question about I/O capacity

    Posted Tue February 16, 2021 12:32 PM
    Here is the response I got back from development:

    HI,

    Its using this page to work out the I/O capability of the storage pool:

    https://www.ibm.com/support/knowledgecenter/sl/ST3FR7_8.3.1/com.ibm.fs7200_831.doc/svc_balancedstorsubsys_23lkme.html

    These guidelines are ok if you are using HDD (fdoesn't matter what type - the calculations are not that precise), but not really applicable if you are using SSD.


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    BYRON GROSSNICKLE
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  • 5.  RE: question about I/O capacity

    Posted Wed February 17, 2021 07:13 AM
    this is from the Redbook, as you can see it states that each SSD is capable of 20000 iops, and probably an FCM is capable of 30000 or more, that makes these calculations in most cases irrelevant nowadays




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    ROGER ERIKSSON
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