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  • 1.  LRUs Writes / Chunk Writes

    Posted Tue November 16, 2021 11:20 AM

    Hello

    Reading Onstat -F, there are LRUs writes more than Chunk writes 

    should LRUs Writes be 0 or at least less than chunk writes ?

    Thanks :)


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    John Smith
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  • 2.  RE: LRUs Writes / Chunk Writes

    Posted Tue November 16, 2021 12:40 PM
    John:

    That's an open debate.
    • Chunk writes are more efficient overall for the storage system
    • LRU writes minimize the overhead of checkpoints and reduce the number of chunk writes which can overwhelm the system

    Mostly I know that when I tune a system to be about 70-75% LRU writes it runs faster. Especially for OLTP workloads, but bulk loads type workload also to some extent.

    Art

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    Art S. Kagel, President and Principal Consultant
    ASK Database Management Corp.
    www.askdbmgt.com
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  • 3.  RE: LRUs Writes / Chunk Writes

    Posted Fri December 24, 2021 08:56 AM
    I think it has more to do with the ability of disk IOPs.
    If the IOPs capability of the disk is very good, you need to adjust the LRU a little larger and make use of the write efficiency of chunk.
    If the IOPs performance is poor, it is recommended to adjust the LRU lower to reduce the transaction blocking caused by CKPT.

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    ZhiWei Cui
    GBASE
    ShiJiaZhuang
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  • 4.  RE: LRUs Writes / Chunk Writes

    Posted Fri December 24, 2021 09:14 AM
    Well taken points! I agree. 

    But my point holds that for OLTP workloads, heavier LRU writes versus chunk writes is better, while for bulk load workloads, a more balanced or even chunk write heavy configuration is better. 

    You are correct, one has to tune for the hardware, but also for the workload. Everything we do as DBAs involves tradeoffs.

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    Art S. Kagel, President and Principal Consultant
    ASK Database Management Corp.
    www.askdbmgt.com
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