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From "Kleegrewe, Christian" <christian.kleegr...@siemens.com>
Subject RE: distribution of regions to servers
Date Wed, 08 Jun 2011 10:04:19 GMT
Hi geoff,

Since hbase balances not at table but at cluster basis it may happen that all the regions
for one table are located at the same region server. The reason for this may be the way hbase
does table splits. If a region exceeds the configured maximum size the region is split into
two, but both resulting regions are on the same region server. In the background there is
a load balancer running that copies regions between region servers in case that the cluster
gets unbalanced. The region that is copied does not necessarily belong to the table that you
are actually creating. It seems to me that the regions copied for balancing in most cases
do not belong to the table that is currently created but there is a simple workaround, if
you want a balancing at table level you should disable all the other tables when generating
a the new table. 

regards

Christian

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-----Original Message-----
From: Geoff Hendrey [mailto:ghendrey@decarta.com] 
Sent: Tuesday, June 07, 2011 8:34 PM
To: hbase-user@hadoop.apache.org
Subject: distribution of regions to servers

I have a table with a hundred or so regions. When I look in the hbase
web ui, I see that all the regions are on one server. Of course we have
many other tables and lots of data. Some tables seem to distribute their
regions amongst many servers. 

 

I know there probably isn't a "pat" answer to this but: wouldn't I want
a large table with many regions to be distributed across many machines?
Just curious to understand the nuance. If I *do* want a uniform
distribution of regions to servers, how would I achieve it?

 

-geoff


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