Database Reference
In-Depth Information
The balancer runs until the cluster is balanced, it cannot move any more blocks, or it loses
contact with the namenode. It produces a logfile in the standard log directory, where it
writes a line for every iteration of redistribution that it carries out. Here is the output from
a short run on a small cluster (slightly reformatted to fit the page):
Time Stamp Iteration# Bytes Already Moved ...Left To Move
...Being Moved
Mar 18, 2009 5:23:42 PM 0 0 KB 219.21
MB 150.29 MB
Mar 18, 2009 5:27:14 PM 1 195.24 MB 22.45
MB 150.29 MB
The cluster is balanced. Exiting...
Balancing took 6.072933333333333 minutes
The balancer is designed to run in the background without unduly taxing the cluster or in-
terfering with other clients using the cluster. It limits the bandwidth that it uses to copy a
block from one node to another. The default is a modest 1 MB/s, but this can be changed
by setting the
dfs.datanode.balance.bandwidthPerSec
property in
hdfs-
site.xml
, specified in bytes.
