[HDFS-4960] Unnecessary .meta seeks even when skip checksum is true

• Type: Bug
• Status: Patch Available
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.1.0-beta, 3.0.0-alpha1
• Labels: BB2015-05-TBR
• Assignee: Varun Sharma
• Reporter: Varun Sharma
• Created: 07/Jul/13 16:35
• Updated: 12/May/16 18:18

Description

While attempting to benchmark an HBase + Hadoop 2.0 setup on SSDs, we found unnecessary seeks into .meta files, each seek was a 7 byte read at the head of the file - this attempts to validate the version #. Since the client is requesting no-checksum, we should not be needing to touch the .meta file at all.

Since the purpose of skip checksum is to also avoid the performance penalty of the extra seek, we should not be seeking into .meta if skip checksum is true

Issue Links

• is related to: HDFS-5634 allow BlockReaderLocal to switch between checksumming and not
• is related to: HDFS-4710 SCR should honor dfs.client.read.shortcircuit.buffer.size even when checksums are off