[HDFS-6186] Pause deletion of blocks when the namenode starts up

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.5.0
• Component/s: namenode
• Hadoop Flags: Reviewed
• Assignee: Jing Zhao
• Reporter: Suresh Srinivas
• Created: 02/Apr/14 17:29
• Updated: 21/Apr/15 03:57
• Resolved: 13/May/14 18:42

Description

HDFS namenode can delete blocks very quickly, given the deletion happens as a parallel operation spread across many datanodes. One of the frequent anxieties I see is that a lot of data can be deleted very quickly, when a cluster is brought up, especially when one of the storage directories has failed and namenode metadata was copied from another storage. Copying wrong metadata would results in some of the newer files (if old metadata was copied) being deleted along with their blocks.

HDFS-5986 now captures the number of pending deletion block on namenode webUI and JMX. I propose pausing deletion of blocks for a configured period of time (default 1 hour?) after namenode comes out of safemode. This will give enough time for the administrator to notice large number of pending deletion blocks and take corrective action.

Thoughts?

Issue Links

• is related to: HDFS-6385 Show when block deletion will start after NameNode startup in WebUI
• is related to: HDFS-8193 Add the ability to delay replica deletion for a period of time
• relates to: HDFS-6493 Change dfs.namenode.startup.delay.block.deletion to second instead of millisecond