https://community.cloudera.com/t5/Support-Questions/Copying-Data-to-HDFS-takes-too-much-time/m-p/164629#M126996 <P><A rel="user" href="https://community.cloudera.com/users/1348/hari.html" nodeid="1348">@hari kiran</A></P><P> There might be network issue</P><PRE>SYMPTOM: Reading/writing of data with HDFS --put, ROOT CAUSE: The message "Slow-BlockReceiver-write-packet-to-mirror" is normally an indication that there is a problem with with underlying networking infrastructure. SOLUTION: Ensure from the OS level that the networking as well as NIC parameters are set up correctly. - verify that MTU value set up as expected - communication mode is correct (full-duplex) - there are not too many errors at the interface level (dropped/overruns) COMMANDS TO USE FOR DEBUGGING: #dmesg &lt;-- identify issues with NIC device driver #ifconfig -a &lt;-- MTU, errorrs (dropped packets/buffer overruns) #ethtool ethX &lt;-- identify/set speed/ negotiation mode/ duplex setting for the inferface In addition, running iperf between datanodes will highlight overall networks transfer issues. #iperf -s (server) #iperf -c 10.1.1.1 -f m -d (client) </PRE> Tue, 24 May 2016 17:13:30 GMT sshimpi 2016-05-24T17:13:30Z