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From Fang Zhou <timchou....@gmail.com>
Subject How can I get the memory usage in Namenode and Datanode?
Date Sat, 21 Feb 2015 20:54:53 GMT
Hi All,

I want to test the memory usage on Namenode and Datanode.

I try to use jmap, jstat, proc/pid/stat, top, ps aux, and Hadoop website interface to check
the memory.
The values I get from them are different. I also found that the memory always changes periodically.
This is the first thing confused me.

I thought the more files stored in Namenode, the more memory usage in Namenode and Datanode.
I also thought the memory used in Namenode should be larger than the memory used in each Datanode.
However, some results show my ideas are wrong.
For example, I test the memory usage of Namenode with 6000 and 1000 files.
The "6000” memory is less than “1000” memory from jmap’s results. 
I also found that the memory usage in Datanode is larger than the memory used in Namenode.

I really don’t know how to get the memory usage in Namenode and Datanode.

Can anyone give me some advices?

Thanks,
Tim
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