[HDFS-7788] Post-2.6 namenode may not start up with an image containing inodes created with an old release.

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 2.7.0, 2.6.1, 3.0.0-alpha1
• Labels: 2.6.1-candidate
• Target Version/s: 2.7.0
• Hadoop Flags: Reviewed
• Assignee: Rushabh Shah
• Reporter: Kihwal Lee
• Created: 12/Feb/15 18:01
• Updated: 30/Aug/16 01:39
• Resolved: 20/Feb/15 15:11

Description

Before HDFS-4305, which was fixed in 2.1.0-beta, clients could specify arbitrarily small preferred block size for a file including 0. This was normally done by faulty clients or failed creates, but it was possible.

Until 2.5, reading a fsimage containing inodes with 0 byte preferred block size was allowed. So if a fsimage contained such an inode, the namenode would come up fine. In 2.6, the preferred block size is required be > 0. Because of this change, the image that worked with 2.5 may not work with 2.6.

If a cluster ran a version of hadoop earlier than 2.1.0-beta before, it is under this risk even if it worked fine with 2.5.