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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15249) Provide lower bound on number of regions in region normalizer for pre-split tables
Date Thu, 11 Feb 2016 16:04:18 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15249?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15142935#comment-15142935
] 

stack commented on HBASE-15249:
-------------------------------

bq. How about giving regions whose write requests are in the bottom 10% (can make this configurable)
?

Above is totally arbitrary. If a region is getting 100 hits a second, thats 10% of 1k -- you'd
merge it because it is getting too little load?

bq. After some time, AMS stopped working because region normalizer merged the regions into
few big regions which were not able to serve high read / write load. This is a big problem
since the write requests flood the regions faster than the splits can happen resulting in
poor performance.

Numbers? How many regions was too little? What was the hit rate that overwhelmed? What did
the normalizer do? It merged up how many regions in how much time?

The problem here is that the time between presplit and the load coming on was too long? The
normalizer merged up the regions  before the load came on? 

> Provide lower bound on number of regions in region normalizer for pre-split tables
> ----------------------------------------------------------------------------------
>
>                 Key: HBASE-15249
>                 URL: https://issues.apache.org/jira/browse/HBASE-15249
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Ted Yu
>            Assignee: Ted Yu
>         Attachments: HBASE-15249.v1.txt, HBASE-15249.v2.txt
>
>
> AMS (Ambari Metrics System) developer found the following scenario:
> Metrics table was pre-split with many regions on large cluster (1600 nodes).
> After some time, AMS stopped working because region normalizer merged the regions into
few big regions which were not able to serve high read / write load.
> This is a big problem since the write requests flood the regions faster than the splits
can happen resulting in poor performance.
> We should consider setting reasonable lower bound on region count.
> If the table is pre-split, we can use initial region count as the lower bound.



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