Hi Gautam, Thank's for quick response. As i told you before we have problem with HDFS block, currently our HDFS block reach to 58 millions with storage occupied equal to 500TB it's not quite ideal. NN memory capacity is about 64GB and we  set 32GB  for NN heap. Last time we change dfs.namenode.checkpoint.txns at the same time with dfs.image.compress from default 44K to 1000K because, we thought when the system often do checkpoint thats lead namenode service become bad as CM report through email. About your question JT pause only began when you turned on compression of fsimage?. We not sure about that cause the mapreduce pause never like now until 10 minutes,  whether it happens or not we do not notice. Does only increase NN heap memory or there are other alternatives that we can tune related with hadoop parameters will reduce load HDFS and will bring back mapreduce to normal during checkpoint ? regards, i9um0   ... View more

The map task's local output is not stored within HDFS, rather in temporary directories on that specific node (see property mapreduce.cluster.local.dir) written using standard file I/O https://hadoop.apache.org/docs/r2.2.0/hadoop-mapreduce-client/hadoop-mapreduce-client-core/mapred-default.xml ... View more