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From Marcus Eriksson <krum...@gmail.com>
Subject Re: What is the cons of changing LCS fanout option to 100 or even bigger?
Date Tue, 18 Sep 2018 11:54:32 GMT
problem would be that for every file you flush, you would recompact all of
L1 - files are flushed to L0, then compacted together with all overlapping
files in L1.

On Tue, Sep 18, 2018 at 4:53 AM 健 戴 <daijian@me.com.invalid> wrote:

> Hi,
>
> I have one table having 2T data saved in c* each node.
> And if using LCS, the data will have 5 level:
>
>
>    - L1: 160M * 10 = 1.6G
>    - L2: 1.6G * 10 = 16G
>    - L3: 16G * 10 = 160G
>    - L4: 160G * 10 = 1.6T
>    - L5: 1.6T * 10 = 16T
>
> When I looking into the source code, I found an option: fanout_size.
>
> The default value is 10. What about change this value to 100? Then the
> level will reduce to 3:
>
>    - L1: 160M * 100 = 16G
>    - L2: 16G * 100 = 1.6T
>    - L3: 1.6T * 100 = 160T
>
> Or even could I set this to 10000? And all files are in a same level.
> Should it be better then?
> What is the cons of the bigger value of this option?
>
> Thanks for your help.
>
>
> Jian
>

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