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From 郭冲 <guochongh...@126.com>
Subject Re:Re: how to select the position of a block
Date Wed, 07 Dec 2011 06:37:58 GMT


isGoodTarget() in  ReplicationTargetChooser.java  judge if a node is a good node, it will
consider the disk space , load , and the rack which it located has too much nodes or not .Thanks!
 
At 2011-12-07 13:01:26,"Harsh J" <harsh@cloudera.com> wrote:
>Moving discussion to hdfs-dev.
>
>DataNodes report disk usage (space) and current transfer thread counts (load) periodically
to the NameNode. NameNode uses this information to make a decision while building the pipeline
DNs for your client request. I believe the class is called something like ReplicationTargetChooser
(off the top of my mind), and you can take a look at the logic involved there in selecting
any form of node (isGoodTarget or summat). Then work your way downwards to see how the information
flows.
>
>On 07-Dec-2011, at 8:36 AM, 郭冲 wrote:
>
>> Hadoop:The Definitive Guide  said that when the client is out of the cluster, hadoop
will select the storage position of a block randomly,but it will not select the datanode which
is too busy or too full.
>> 
>> so i want to kown that  how hadoop judge or measure a datanode is full or not?
>
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