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From: Eric Pogrelis <daywalker13@gmail.com>
Date: Mon, 19 Sep 2016 09:35:14 -0500
Message-ID: <CAJGtNXJNgkMocsOPOEaqaHPTcS+EMYJ=vdemLxT-d3QLGRfDDA@mail.gmail.com>
Subject: Re: [Urgent] - HBase - Addition of new region servers - Presplit based
To: cdh-user@cloudera.org
Cc: user@hbase.apache.org
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archived-at: Mon, 19 Sep 2016 15:40:26 -0000

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V,

Regionservers (what you said you're adding) and regions are two different
things. If you are manually splitting such that you have only 3 regions,
then if you add additional regionservers, those regionservers may not be
serving any regions. To put that a better way, if you have a single table
with 3 regions, then there are only 4 regions in total -- your 3-region
table + the region for the hbase meta table. So, if you have 5
regionservers but only 4 regions to be served, then one regionserver will
be idle. To take advantage of the additional regionservers you would want
to modify your split such that there are enough regions that all the
regionservers have a region to serve.

On Mon, Sep 19, 2016 at 9:16 AM, Viswanathan J <jayamviswanathan@gmail.com>
wrote:

> Thanks Eric for the update.
>
> Re-balancing will happen automatically, but while writing/reading in HBase
> we're forming the rowkey by pre-splitting based on 3 regions. So if I add
> new regions to the cluster while reading data from 5 rs it will be impacted
> because written data only on 3 regions?
>
> Thanks,
> Viswa.J
>
> On Sun, Sep 18, 2016 at 11:17 PM, Eric Pogrelis <daywalker13@gmail.com>
> wrote:
>
>> Absent other changes, the existing regions will simply be re-balanced
>> across the new region server count of 5.
>>
>> On Fri, Sep 16, 2016 at 9:46 AM, Viswanathan J <
>> jayamviswanathan@gmail.com> wrote:
>>
>>> Hi,
>>>
>>> Currently I have 3 region servers and reading/storing data based on
>>> pre-split(hashing). If I need to add 2 more region servers how it will
>>> impact while reading and writing the data. Because currently pre-split
>>> hashing only based on 3 rs.
>>>
>>> Please help.
>>>
>>> --
>>> Regards,
>>> Viswa.J
>>>
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>>>
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>
>
>
> --
> Regards,
> Viswa.J
>
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