[HADOOP-11847] Enhance raw coder allowing to read least required inputs in decoding

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: HDFS-7285
• Component/s: io
• Labels: BB2015-05-TBR
• Target Version/s: HDFS-7285
• Hadoop Flags: Reviewed
• Assignee: Kai Zheng
• Reporter: Kai Zheng
• Created: 20/Apr/15 00:20
• Updated: 30/Sep/15 19:38
• Resolved: 26/May/15 06:49

Description

This is to enhance raw erasure coder to allow only reading least required inputs while decoding. It will also refine and document the relevant APIs for better understanding and usage. When using least required inputs, it may add computating overhead but will possiblly outperform overall since less network traffic and disk IO are involved.

This is something planned to do but just got reminded by zhz' s question raised in HDFS-7678, also copied here:

Kai Zheng I have a question about decoding: in a (6+3) schema, if block #2 is missing, and I want to repair it with blocks 0, 1, 3, 4, 5, 8, how should I construct the inputs to RawErasureDecoder#decode?

With this work, hopefully the answer to above question would be obvious.

Issue Links

• is duplicated by: HADOOP-11908 Erasure coding: Should be able to encode part of parity blocks.