[HDFS-9440] Improve BlockPlacementPolicyDefault's to be able to rebalance when picking of excess replicas

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Unassigned
• Reporter: Xiao Chen
• Created: 19/Nov/15 01:28
• Updated: 22/May/19 08:37

Description

The test case used in HDFS-9313 and HDFS-9314 identified the limitation of excess replica picking. If the current replicas are on

{SSD(rack 1), DISK(rack 3), DISK(rack 3), DISK(rack 3)}

and the storage policy changes to HOT_STORAGE_POLICY_ID, BlockPlacementPolicyDefault's won't be able to delete SSD replica, because deleting the SSD on rack 1 will violate the block placement policy.

Issue Links

• relates to: HDFS-9313 Possible NullPointerException in BlockManager if no excess replica can be chosen
• relates to: HDFS-9314 Improve BlockPlacementPolicyDefault's picking of excess replicas