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From Jean-Daniel Cryans <jdcry...@apache.org>
Subject Re: Can I pick which region server to store my row?
Date Wed, 06 Oct 2010 16:54:31 GMT
Like Stack said, it's available in 0.90 which we're currently wrapping
up (so not in 0.20.x).

Distributing regions and distributing blocks is orthogonal (ish, but
for this discussion let's not mix the two together), the former being
assumed by the HBase master and the latter being assumed by the
Namenode. Maybe this blog post can help you understanding how HBase
uses HDFS http://www.larsgeorge.com/2009/10/hbase-architecture-101-storage.html

J-D

On Tue, Oct 5, 2010 at 8:38 PM, William Kang <weliam.cloud@gmail.com> wrote:
> So, I can use the 'move' command to manually balance the load? Is this
> available to 0.20.6? Was there any automatic balance mechanism in hbase
> before if the replicated block is not for load distribution purpose? Thanks.
>
>
> William
>
> On Tue, Oct 5, 2010 at 11:19 PM, Stack <stack@duboce.net> wrote:
>
>> In 0.90, you can turn off the balancer and then distribute the regions
>> any way you wish with new 'move' command.
>> St.Ack
>>
>> On Tue, Oct 5, 2010 at 8:13 PM, Jean-Daniel Cryans <jdcryans@apache.org>
>> wrote:
>> > A row is always served a single region, so the question is more about
>> > region distribution. In 0.20 and 0.89 you have no control over that
>> > (the best you can do is calling close_region in the shell, where is
>> > the region will be moved is "random"), but things are getting better
>> > in 0.90 where you'll be able to move regions manually.
>> >
>> > HBase doesn't create multiple copies of HFiles to distribute load,
>> > what happens is each block is replicated 3 times by HDFS and this is
>> > invisible to HBase. This is done for data safety rather than
>> > distributing the load.
>> >
>> > J-D
>> >
>> > On Tue, Oct 5, 2010 at 8:05 PM, William Kang <weliam.cloud@gmail.com>
>> wrote:
>> >> Hi folks,
>> >> I have a general question about Hbase. Can we pick which region server
>> we
>> >> want to save a particular row? The reason I am asking this is because
>> >> sometimes we want to manually balance region servers' load. If we could
>> >> assign particular rows to particular region servers, we can have that
>> >> control. I understand that Hbase will balance its load automatically by
>> >> create multiple copies of hfiles in HDFS. But, we do want to have more
>> >> control over that. Is it possible or is it already in Hbase but we
>> didn't
>> >> find it? Many thanks.
>> >>
>> >>
>> >> William
>> >>
>> >
>>
>

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