4. Network Parameters Tuning:

Network parameters tuning also helps to get performance boost! This is kinda risky stuff because if you are working on remote server and you did a mistake while updating Network parameters then there can be a connectivity loss and you may not be able to connect to that server again unless you correct the configuration mistake by taking IPMI/iDrac/iLo console etc. Modify the parameters only when you know what you are doing

Modifying the net.core.somaxconn to 1024 from default value of 128 will help Hadoop by as this changes will have increased listening queue between the master and slave services so ultimately number of connections between master and slaves will be higher than before.

Command to modify net.core.somaxconnection:

sysctl –w net.core.somaxconn=1024

To make above change permanent, simple add below variable value at the end of /etc/sysctl.conf

net.core.somaxconn=1024

MTU Settings:

Maximum transmission unit. This value indicates the size which can be sent in a packet/frame over TCP. By default MTU is set to 1500 and you can tune it have its value=9000, when value of MTU is greater than its default value then it’s called as Jumbo Frames.

Command to change value of MTU:

You need to add MTU=9000 in /etc/sysconfig/network-scripts/ifcfg-eth0 or whatever your eth device name. Restart the network service in order to have this change in effect.

Note – Before modifying this value please make sure that all the nodes in your cluster including switches are supported for jumbo frames, if not then *PLEASE DO NOT ATTEMPT THIS*