[HDFS-16613] EC: Improve performance of decommissioning dn with many ec blocks

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.4.0
• Fix Version/s: 3.4.0
• Component/s: ec, erasure-coding, namenode
• Labels: pull-request-available
• Assignee: caozhiqiang
• Reporter: caozhiqiang
• Created: 31/May/22 16:18
• Updated: 19/Dec/22 22:25
• Resolved: 16/Jun/22 18:11

Description

In a hdfs cluster with a lot of EC blocks, decommission a dn is very slow. The reason is unlike replication blocks can be replicated from any dn which has the same block replication, the ec block have to be replicated from the decommissioning dn.

The configurations dfs.namenode.replication.max-streams and dfs.namenode.replication.max-streams-hard-limit will limit the replication speed, but increase these configurations will create risk to the whole cluster's network. So it should add a new configuration to limit the decommissioning dn, distinguished from the cluster wide max-streams limit.

Issue Links

• is related to: HDFS-16874 Improve DataNode decommission for Erasure Coding
• is related to: HDFS-16663 EC: Allow block reconstruction pending timeout refreshable to increase decommission performance
• relates to: HDFS-16846 EC: Only EC blocks should be effected by max-streams-hard-limit configuration
• links to: GitHub Pull Request #4391
• links to: GitHub Pull Request #4391
• links to: GitHub Pull Request #4398