[HDFS-1940] Datanode can have more than one copy of same block when a failed disk is coming back in datanode

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 0.20.204.0
• Component/s: datanode
• Assignee: Bharath Mundlapudi
• Reporter: Rajit Saha
• Created: 14/May/11 03:06
• Updated: 06/Apr/12 22:07

Description

There is a situation where one datanode can have more than one copy of same block due to a disk fails and comes back after sometime in a datanode. And these duplicate blocks are not getting deleted even after datanode and namenode restart.

This situation can only happen in a corner case , when due to disk failure, the data block is replicated to other disk of the same datanode.

To simulate this scenario I copied a datablock and the associated .meta file from one disk to another disk of same datanode, so the datanode is having 2 copy of same replica. Now I restarted datanode and namenode. Still the extra data block and meta file is not deleted from the datanode

ls -l `find /grid/

{0,1,2,3}

/hadoop/var/hdfs/data/current -name blk_*`
rw-rr- 1 hdfs users 7814 May 13 21:05 /grid/1/hadoop/var/hdfs/data/current/blk_1727421609840461376
rw-rr- 1 hdfs users 71 May 13 21:05 /grid/1/hadoop/var/hdfs/data/current/blk_1727421609840461376_579992.meta
rw-rr- 1 hdfs users 7814 May 13 21:14 /grid/3/hadoop/var/hdfs/data/current/blk_1727421609840461376
rw-rr- 1 hdfs users 71 May 13 21:14 /grid/3/hadoop/var/hdfs/data/current/blk_1727421609840461376_579992.meta

Issue Links

• is related to: HDFS-2137 Datanode Disk Fail Inplace