Reduce job pending in HFileOutputFormat

Reduce job pending in HFileOutputFormat

I am using
Hbase:0.92.1-cdh4.1.2, and Hadoop:2.0.0-cdh4.1.2
I have a mapreduce program that will load data from HDFS to HBase using
HFileOutputFormat in cluster mode. In that mapreduce program i'm using
HFileOutputFormat.configureIncrementalLoad() to bulk load a 800000 record
data set which is of 7.3GB size and it is running fine, but it's not
running for 900000 record data set which is of 8.3GB.
In the case of 8.3GB data my mapreduce program have 133 maps and one
reducer,all maps completed successfully.My reducer status is always in
Pending for a long time. There is nothing wrong with the cluster since
other jobs are running fine and this job also running fine upto 7.3GB of
data.
What could i be doing wrong? How do I fix this issue?