[HDFS-13157] Do Not Remove Blocks Sequentially During Decommission

• Type: Improvement
• Status: Patch Available
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.0.0
• Component/s: datanode, namenode
• Assignee: David Mollitor
• Reporter: David Mollitor
• Created: 16/Feb/18 16:57
• Updated: 01/Aug/20 02:59

Description

From what I understand of DataNode decommissioning it appears that all the blocks are scheduled for removal in order.. I'm not 100% sure what the ordering is exactly, but I think it loops through each data volume and schedules each block to be replicated elsewhere. The net affect is that during a decommission, all of the DataNode transfer threads slam on a single volume until it is cleaned out. At which point, they all slam on the next volume, etc.

Please randomize the block list so that there is a more even distribution across all volumes when decommissioning a node.

Issue Links

• links to: GitHub Pull Request #1391