[HADOOP-2148] Inefficient FSDataset.getBlockFile()

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.14.0
• Fix Version/s: 0.17.0
• Assignee: Konstantin Shvachko
• Reporter: Konstantin Shvachko
• Created: 03/Nov/07 00:12
• Updated: 08/Jul/09 16:42
• Resolved: 19/Mar/08 22:48

Description

FSDataset.getBlockFile() first verifies that the block is valid and then returns the file name corresponding to the block.
Doing that it performs the data-node blockMap lookup twice. Only one lookup is needed here.
This is important since the data-node blockMap is big.

Another observation is that data-nodes do not need the blockMap at all. File names can be derived from the block IDs,
there is no need to hold Block to File mapping in memory.