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From divye sheth <divs.sh...@gmail.com>
Subject Re: DFS Balancer with Hbase
Date Tue, 04 Mar 2014 14:03:01 GMT
Thanks Bharath, I had a look at the jira and the fix version is 0.94.0. I
am using 0.94.2, I assume this should already be a part of Hbase. Is the
assumption correct? If no do I have to make these changes in hbase-site.xml?

Note: We have not run major_compaction for any of the tables so far. Will
doing so mitigate the issue to some extent?

Thanks
Divye Sheth


On Tue, Mar 4, 2014 at 7:10 PM, Bharath Vissapragada
<bharathv@cloudera.com>wrote:

> Did you check the per table balancer? (HBASE-3373),
> hbase.master.loadbalance.bytable=true
>
> Default load balancer just balances based on metric region count per table
> which can result in all big regions from a single table falling on one RS
> thus overloading it. This might be one of the reasons and you can confirm
> it from current region assignment.
>
> Do a major compaction after enabling this setting and regions are balanced
> so that the newly written hfiles are uniformly distributed.
>
>
>
>
> On Tue, Mar 4, 2014 at 6:54 PM, divye sheth <divs.sheth@gmail.com> wrote:
>
> > Thanks Jean, but why does only a couple of RS get loaded with data? We
> are
> > seeing out of 5 only 2 datanodes have around 90% of disk usage. Where as
> > the rest are at around 40%.
> >
> > We have run the hbase balancer, and on an average we have around 500
> > regions per regionserver and a total of 5 RS's. We have even disabled
> > number of tables which are not required and currently the count of
> > regions/RS is around 120.
> >
> > Another question that comes to my mind is. Somewhere down the line the
> > Hadoop cluster tends to be imbalanced and lead to 100% disk utilization
> and
> > the balancer activity has to be triggered, how do you guys handle such
> > problem in your hbase cluster?
> >
> > Just a thought, could we execute the DFS balancer and after the balancing
> > activity trigger major compaction for each table?
> >
> > Thanks
> > Divye Sheth
> >
> >
> > On Tue, Mar 4, 2014 at 6:45 PM, Jean-Marc Spaggiari <
> > jean-marc@spaggiari.org
> > > wrote:
> >
> > > Hi Divye,
> > >
> > > the DFS balancer is that last thing you want to run in your HBase
> > > cluster.That will break all the data locallity for the compacted
> regions.
> > >
> > > On compaction, a region write the files on the local server first, then
> > the
> > > 2 other replicates are going on different datanodes. so on read, HBase
> > can
> > > garantee that data is read from local datanode dans not from another
> > > datanode over the network.
> > >
> > > Have you run the HBase balancer? How many regions do you have per
> region
> > > server?
> > >
> > > JM
> > >
> >
>
>
>
> --
> Bharath Vissapragada
> <http://www.cloudera.com>
>

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