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From Ramiya V <Ramiy...@persistent.co.in>
Subject FW: Issues with performance on Hadoop/Hive
Date Wed, 02 Sep 2009 06:47:02 GMT

I just wanted to add that I know 45GB data is really less to test the performance of Hadoop/Hive
as it needs data in Terabytes. Actually I have to implement a  POC and it requires me to test
only 45GB of data. Please let me know if the performance can be improved.


From: Ramiya V
Sent: Wednesday, September 02, 2009 10:38 AM
To: common-user@hadoop.apache.org
Subject: Issues with performance on Hadoop/Hive


I have set up a 4 (physical) nodes Hadoop cluster. Configuration: 2GB RAM each machine. Currently
am using the sub-project Hive for firing queries on 45GB of data. I have certain queries that
need to be resolved:-

1) The performance that I am getting with the above setup is quite bad. It takes app 39 minutes
for simple select query (with where clause). I have set the mapred.map.tasks=13 and mapred.reduce.tasks=7.
Is this setting good enough for the above setup? Are there any significant configuration parameters
I need to set for getting a better performance on Hive?

2) Does anybody know how exactly the data on HDFS is distributed across nodes in a cluster?
Also when we load the tables in Hive (by firing Load command on master node),how and where
is the data placed on HDFS in a cluster?

3) How and when does the data replication for HDFS take place in a cluster? Currently I have
set the dfs replication factor=1. How does this affect the performance?

4) Does adding a Virtual Machine to a physical machine cluster bring about significant degradation
in the performance?

Please let me know asap.


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