描述：
If a large directory is deleted and namenode is immediately restarted, there are a lot of blocks that do not belong to any file. This results in a log:
2014-11-08 03:11:45,584 INFO BlockStateChange (BlockManager.java:proce***eport(1901)) - BLOCK* proce***eport: blk_1074250282_509532 on 172.31.44.17:1019 size 6 does not belong to any file.
This log is printed within FSNamsystem lock. This can cause namenode to take long time in coming out of safemode.
One solution is to downgrade the logging level.
解決方案
tail -f /var/log/hadoop/hdfs/hdfs-namenode.log
http://<namenode:50070>/logLevel
Input "BlockStateChange" and Level is "WARN" and then click "Set Log Level" button
wait 2~3 mins. it works and performance is fine.