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From Ninad Raut <hbase.user.ni...@gmail.com>
Subject Re: Small issues regarding hadoop/hbase
Date Mon, 11 May 2009 06:08:34 GMT
>
> 2. how do you dynamically add and remove nodes in the cluser without
> disturbing the existing map-reduce jobs (on EC2).



Are there datanodes and tasktrackers running on the same node as the
regionserver?  If so, it may be a little tricky coordinating them all.  You
could try shutting down the regionserver with a ./bin/hbase-daemon.sh
regionserver stop (IIRC) and then just let the server go.

Will this cause any loss of data.? How will the data loss be handled.

On Wed, May 6, 2009 at 8:42 PM, stack <stack@duboce.net> wrote:

> On Wed, May 6, 2009 at 3:08 AM, Rakhi Khatwani <rakhi.khatwani@gmail.com
> >wrote:
>
> >
> > 1. i wanna scan a table, but the table is really huge. so i want the
> result
> > of the scan to some file so that i can analyze it. how do we go about
> it???
> >
>
>
> If your table is really huge, I presume your scan output huge too.
>
> You should write a MapReduce job.  See TableInputFormat in the hbase mapred
> package.  See RowCounter in same package for an example pulling rows in a
> MR
> job from hbase.
>
>
>
> >
> > 2. how do you dynamically add and remove nodes in the cluser without
> > disturbing the existing map-reduce jobs (on EC2).
>
>
>
> Are there datanodes and tasktrackers running on the same node as the
> regionserver?  If so, it may be a little tricky coordinating them all.  You
> could try shutting down the regionserver with a ./bin/hbase-daemon.sh
> regionserver stop (IIRC) and then just let the server go.
>
>
> >
> >
> > 3. suppose my dfs replication is 3. (which implies that i have 3 copies
> of
> > data in some other location). how do i access other two copies. or how do
> i
> > find out in which machines are the other copies kept?
>
>
>
> A file is made of blocks in hdfs.  Its the blocks that are replicated.  To
> see where the replicas are, you could enable debug logging.  You might be
> able to see where all are in the hdfs UI, I'm not sure.
>
>
> >
> >
> > 4. If my hbase master fails, is there any way i can set another node as
> my
> > hbase master without disturbing my current map-reduce jobs??
> >
>
> Coming in 0.20.0 hbase.
>
> St.Ack
>

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