Change MTU vmkernel NFS datastore from 1500 to 9000

[yokayoka]

if i want to change MTU VMkernel NFS Datastore from 1500 to 9000, is it possible to do online? or I need to enter maintenance mode first than change the MTU?

Thanks,

[LucianoPatrão · Accepted solution]

No you do not need any downtime to do this work.

But be careful before changing this. Make sure all your Storage network(network interfaces, switches, ports, etc.) have the same MTU before you changed. If not, doing this on production if they are not aligned you will have issues with the datastores.

But changing MTU is at Virtual Switch and Port Group and vmkernel. Check all the paths.

But if were me, I will put the ESXi host in maintenance mode before I do those changes.

[MaxB]

An online change should be possible.

May you have also to change the MTU in your hostprofile - if you are using them.

Just as additional hint. 

Anyways take care of the points that have been mentioned earlier.

[yokayoka]

thanks for your answer. I have one question again.  so if I have VM in vsan datastore and VM in nfs datastore then I changed the only VMkernel for NFS traffic, if something bad happend, it only impact to NFS datastote right?

[MaxB]

imho yes.

In case of you have two seperate VMkernel ports. one for vSAN and one for NFS.

[LucianoPatrão]

The only with MTU is when you are using bigger packages than you have set in your network.

Example: All your network is set to 9000 MTU, but vSAN and NFS are still set to 1500.

This works without any issue, if you need to change vSAN to 9000 is ok. You just need to change the vmkernel to work with 9000. NFS vmkernel will still be working with 1500.

Now if you have a network set to 1500 MTU and you are changing any part to work with 9000 then you have a problem since the network cannot handle that packet size and will full queues will cause packet losses when transporting udp packets.