[HADOOP-922] Optimize small reads and seeks

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.10.1
• Fix Version/s: 0.11.0
• Assignee: Dhruba Borthakur
• Reporter: Dhruba Borthakur
• Created: 24/Jan/07 00:13
• Updated: 08/Jul/09 16:42
• Resolved: 30/Jan/07 22:47

Description

A seek on a DFSInputStream causes causes the next read to re-open the socket connection to the datanode and fetch the remainder of the block all over again. This is not optimal.

A small read followed by a small positive seek could re-utilize the data already fetched from the datanode as part of the previous read.

Issue Links

• is related to: HADOOP-519 HDFS File API should be extended to include positional read