[HADOOP-3164] Use FileChannel.transferTo() when data is read from DataNode.

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.18.0
• Hadoop Flags: Reviewed

Release Note

Changed data node to use FileChannel.tranferTo() to transfer block data.

• Assignee: Raghu Angadi
• Reporter: Raghu Angadi
• Created: 03/Apr/08 19:22
• Updated: 08/Jul/09 16:43
• Resolved: 25/Apr/08 00:10

Description

HADOOP-2312 talks about using FileChannel's transferTo() and transferFrom() in DataNode.

At the time DataNode neither used NIO sockets nor wrote large chunks of contiguous block data to socket. Hadoop 0.17 does both when data is seved to clients (and other datanodes). I am planning to try using transferTo() in the trunk. This might reduce DataNode's cpu by another 50% or more.

Once HADOOP-1702 is committed, we can look into using transferFrom().

Issue Links

• relates to: HDFS-281 Explore usage of the sendfile api via java.nio.channels.FileChannel.transfer{To|From} for i/o in datanodes