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From jiang licht <licht_ji...@yahoo.com>
Subject Re: How often namenode dumps in-memory hdfs meta data to disk (dfs.name.dir)?
Date Fri, 25 Jun 2010 17:47:32 GMT
Thanks, I understand in-memory editlog is updated on every change but thought that it was buffered
before been serialized to disk. So, in case of busy writting data into hdfs, namenode is actually
frequently doing disk write, but each time in a small chunk, and at os level, this will be
buffered ...

--Michael

--- On Fri, 6/25/10, Allen Wittenauer <awittenauer@linkedin.com> wrote:

From: Allen Wittenauer <awittenauer@linkedin.com>
Subject: Re: How often namenode dumps in-memory hdfs meta data to disk (dfs.name.dir)?
To: "<common-user@hadoop.apache.org>" <common-user@hadoop.apache.org>
Date: Friday, June 25, 2010, 12:17 PM


On Jun 25, 2010, at 12:24 AM, jiang licht wrote:
> Then, I think that namenode will need to write editlog to disk at a regular interval.

This is incorrect.

> Correct me if I misunderstand anything.

The edits log is updated on every change.  Create a file?  Updated.  Changed permissions? 
Updated.  

> So, how often namenode write any meta data/change to dfs.name.dir?

Constantly.





      
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