[YARN-202] Log Aggregation generates a storm of fsync() for namenode

• Type: Sub-task
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 2.0.2-alpha, 0.23.4
• Fix Version/s: 2.0.3-alpha, 0.23.5
• Assignee: Kihwal Lee
• Reporter: Kihwal Lee
• Created: 06/Nov/12 00:29
• Updated: 03/Sep/14 23:17
• Resolved: 06/Nov/12 18:54

Description

When the log aggregation is on, write to each aggregated container log causes hflush() to be called. For large clusters, this can creates a lot of fsync() calls for namenode.

We have seen 6-7x increase in the average number of fsync operations compared to 1.0.x on a large busy cluster. Over 99% of fsync ops were for log aggregation writing to tmp files.