[HDFS-6000] Avoid saving namespace when starting rolling upgrade

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Component/s: datanode, ha, hdfs-client, namenode
• Hadoop Flags: Reviewed
• Assignee: Jing Zhao
• Reporter: Jing Zhao
• Created: 23/Feb/14 01:26
• Updated: 25/Feb/14 22:01
• Resolved: 25/Feb/14 22:01

Description

Currently when administrator sends the "rollingUpgrade start" command to the active NN, the NN will trigger a checkpoint (the rollback fsimage). This will cause NN not able to serve for a period of time.

An alternative way is just to let the SBN do checkpoint, and rename the first checkpoint after starting the rolling upgrade to rollback image. After the rollback image is on both the ANN and the SBN, administrator can start upgrading the software.