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From Ted Yu <yuzhih...@gmail.com>
Subject Re: several doubts about region split?
Date Wed, 17 Jul 2013 14:05:11 GMT
bq. Does it mean the region which will be splitted is not available anymore?

Right.

bq. What happened to the read and write requests to that region?

The requests wouldn't be served by the hosting region server until daughter
regions become online.

Will try to dig up answer to question #2.
In short, load balancer is supposed to offload one of the daughter regions
if continuous write load incurs.

Cheers

On Wed, Jul 17, 2013 at 6:53 AM, yonghu <yongyong313@gmail.com> wrote:

> Dear all,
>
> From the HBase reference book, it mentions that when RegionServer splits
> regions, it will offline the split region and then adds the daughter
> regions to META, opens daughters on the parent's hosting RegionServer and
> then reports the split to the Master.
>
> I have a several questions:
>
> 1. What does offline means? Does it mean the region which will be splitted
> is not available anymore? What happened to the read and write requests to
> that region?
>
> 2. From the description, if I understand right it means that now the
> RegionServer will contain two Regions (One RegionServer for both daughter
> and parent regions ) instead of one RegionSever for daughter and one for
> parent. If it is, what are the benefits of this approach? Hot-spot problem
> is still there. Moreover, this approach will be a big problem if we use the
> HBase default split approach. Suppose we bulk load data into HBase cluster,
> initially every write request will be accepted by only one RegionServer.
> After some write requests, the RegionServer cannot response any write
> request as it reaches its disk volume threshold. Hence, some data must be
> removed from one RegionSever to the other RegionServer. The question is
> that why we don't do it at the region split time?
>
> Thanks!
>
> Yong
>

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