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https://issues.apache.org/jira/browse/HBASE-21006?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16568474#comment-16568474
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Hari Sekhon edited comment on HBASE-21006 at 8/3/18 4:57 PM:
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Data locality % improves very, very slowly over the course of days after 
rolling restarts, eg. a few percent a day until it comes back up to around 90%.

I suspect this is due to minor compactions re-writing blocks locally and not 
due to region migrations, which would mean that the balancer isn't optimising 
data locality back up.


was (Author: harisekhon):
Data locality % improves very, very slowly over the course of days after 
rolling restarts.

I suspect this is due to minor compactions re-writing blocks locally and not 
due to region migrations, which would mean that the balancer isn't optimising 
data locality back up.

> Balancer - data locality drops hugely after rolling restarts on cluster, not 
> factoring in data locality enough?
> ---------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-21006
>                 URL: https://issues.apache.org/jira/browse/HBASE-21006
>             Project: HBase
>          Issue Type: Improvement
>          Components: Balancer
>    Affects Versions: 1.1.2
>         Environment: HDP 2.6
>            Reporter: Hari Sekhon
>            Priority: Major
>
> After doing rolling restarts of my HBase cluster the data locality drops by 
> 30-40% every time which implies the stochastic balancer is not optimizing for 
> data locality enough, at least not under the circumstance of rolling restarts.
> The stochastic balancer is supposed to take data locality in to account but 
> if this is the case, surely it should move regions back to their original 
> RegionServer and data locality should return back to around where it was, not 
> drop by 30-40% percent every time I need to do some tuning and a rolling 
> restarts.



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