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From Rakhi Khatwani <rakhi.khatw...@gmail.com>
Subject Re: Region Servers going down frequently
Date Wed, 08 Apr 2009 06:29:24 GMT
Hi Amandeep,
                  I have 1GB Memory on each node on ec2 cluster(C1 Medium) .
i am using hadoop-0.19.0 and hbase-0.19.0
well we were starting with 10,000 rows, but later it will go up to 100,000

my map task basically reads an hbase table 'Table1', performs analysis on
each row, and dumps the analysis results into another hbase table 'Table2'.
each analysis task takes about 3-4 minutes when tested on local machine (the
algorithm part.... w/o the map reduce).

i have divided 'Table1' to 30 regions b4 sending it to the map. and set the
maximum number of map tasks to 20.
i have set DataXceivers to 1024 and uLimit to 1024
i am able to process about 300 rows in an hour which i feel quite slow...
how do i increase the performance.

meanwhile i will try settin the dataXceivers to 2048 and increasing the file
limit as you mentioned.


On Wed, Apr 8, 2009 at 11:40 AM, Amandeep Khurana <amansk@gmail.com> wrote:

> 20 nodes is good enough to begins with. How much memory do you have on each
> node? IMO, you should keep 1GB per daemon and 1GB for the MR job like
> Andrew
> suggested.
> You dont necessarily have to separate the datanodes and tasktrackers as
> long
> as you have enough resources.
> 10000 rows isnt big at all from hbase standpoint. What kind of computation
> are you doing before dumping data into hbase? And what versions of Hadoop
> and Hbase are you running?
> There's another thing you should do. Increase the DataXceivers limit to
> 2048
> (thats what I use).
> If you have root privelege over the cluster, then increase the file limit
> to
> 32k (see hbase faq for details).
> Try this out and see how it goes.
> Amandeep Khurana
> Computer Science Graduate Student
> University of California, Santa Cruz
> On Tue, Apr 7, 2009 at 2:45 AM, Rakhi Khatwani <rakhi.khatwani@gmail.com
> >wrote:
> > Hi,
> >      I have a 20 node cluster on ec2(small instance).... i have a set of
> > tables which store huge amount of data (tried wid 10,000 rows... more to
> be
> > added).... but during my map reduce jobs, some of the region servers shut
> > down thereby causing data loss, stop in my program execution and infact
> one
> > of my tables got damaged. when ever i scan the table, i get the could not
> > obtain block error.
> >
> > 1. i want to make the cluster more robust. since it contains a lot of
> data.
> > and its really important that they remain stable.
> > 2. if one of my tables gets damaged (even after restarting dfs n hbase),
> > how
> > do i go about recovering it?
> >
> > my ec2 cluster mostly has the default configuration.
> > with hadoop-site n hbase-site have some entries pertaining to map-reduce
> > (for example. num of map tasks, mapred.task.timeout etc).
> >
> > Your help will be greatly appreciated.
> > Thanks,
> > Raakhi Khatwani
> >

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