how to find the right value of MTU Jumbo frame

[#1]

we take the decision to set jumbo frame on all our linux machines

we have ambari cluster with master machines , workers machines and kafka machines

our switches ( Cisco ) are suitable to Jumbo frame and that fine

but jumbo frame can set as 8000 or 9000 or between them or less then 8000 what is the formula to calculate what is the best MTU value ?

[#2 · Accepted solution]

@Michael Bronson

The value of MTU depends on the network devices that are going to take e part in the communication. like Routers / machines.

The following link explains how to set the MTU value and how to deter mine it's value based on our network devices standards.

Reference:
https://www.tp-link.com/us/article/?faqid=190
http://www.microhowto.info/howto/change_the_mtu_of_a_network_interface.html
http://www.geekprojects.org/2015/07/increase-centos-7s-mtu/

Good visual Explain:

https://www.youtube.com/watch?v=Y6IMlPSl4fI

https://www.youtube.com/watch?v=LeaEmOUVEn0

Important Notes:
- Due to additional complications, VPNs require a different type of MTU test.

- If you have a network with multiple PCs every computer should be set up with the same MTU. Additionally, some PCs may use several Network Adapters or a VPN client adapter on one PC so you must verify you are changing the Network Adapter associated with your broadband service or VPN client.

- The built in PPPoE client for Windows XP uses an MTU that is set to 1480 (1500).

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[#3]

@Jay what is hortonworks recommendation about the MTU value ? ( we have many ambari cluster and we want to know what is the best MTU value )

[#4]

second question , can we set the MTU in way to get the best OS performance ? ,

[#5]

note - all our machines are linux redhat machines

[#6]

@Michael Bronson

Regarding your following query: hortonworks recommendation about the MTU value ?

>>> Unfortunately i did not find any such document/guide which can give the value for MTU on Hortonworks Component cluster. As it's a tuning parameter and it completely depends on how the network equipment's are capable of handling jumbo frames. The value may vary based on N/W equipment's types and type of N/W.

Too large an MTU size may mean retransmission's of packets if the packet encounters a router that can't handle that large a packet.
Too small an MTU size means relatively more header overhead and more acknowledgements that have to be sent and handled.

More than the operating system (like RedHat Linux) it applies to communications protocols and network layers (Datalink Layer/Ethernet frame).

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If your network can support 9000 MTU then you can go ahead with it. You might need to monitor the Network packet drops initially to see there is no issue with N/W device communication.

[#7]

@Jay just one note do you see any coralation between MTU=9000 to less performance , or this is not relevant at all ?