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From ramkrishna vasudevan <ramkrishna.s.vasude...@gmail.com>
Subject Re: Scan problem
Date Mon, 19 Mar 2018 05:14:36 GMT
Hi

First regarding the scans,

Generally the data resides in the store files which is in HDFS. So probably
the first scan that you are doing is reading from HDFS which involves disk
reads. Once the blocks are read, they are cached in the Block cache of
HBase. So your further reads go through that and hence you see further
speed up in the scans.

>> And another question about region split, I want to know which
RegionServer
will load the new region afther splited ,
Will they be the same One with the old region?
Yes . Generally same region server hosts it.

In master the code is here,
https://github.com/apache/hbase/blob/master/hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/SplitTableRegionProcedure.java

You may need to understand the entire flow to know how the regions are
opened after a split.

Regards
Ram

On Sat, Mar 17, 2018 at 9:02 PM, Yang Zhang <zhang.yang.dm@gmail.com> wrote:

> Hello everyone
>
>         I try to do many Scan use RegionScanner in coprocessor, and ervery
> time ,the first Scan cost  about 10 times than the other,
> I don't know why this will happen
>
> OneBucket Scan cost is : 8794 ms Num is : 710
> OneBucket Scan cost is : 91 ms Num is : 776
> OneBucket Scan cost is : 87 ms Num is : 808
> OneBucket Scan cost is : 105 ms Num is : 748
> OneBucket Scan cost is : 68 ms Num is : 200
>
>
> And another question about region split, I want to know which RegionServer
> will load the new region afther splited ,
> Will they be the same One with the old region?  Anyone know where I can
> find the code to learn about that?
>
>
> Thanks for your help
>

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