1

We have a hadoop cluster; some of the machines in the cluster are VM machines and all others are physical machines.

According to documentation, it is better to set MTU=9000 on all machines, but I am not sure if the VM's can support MTU=9000.

2

When using Jumbo frames, all the NICs in a VLAN/netblock must support and be configured to Jumbo frames without exception.

I would stress ALL of them.

In doubt, make plans and make some extensive tests with all the hosts you have.

If the tests are successful, add another NIC to those VMs and create a special VLAN just for the hadoop VMs to transfer data between them.

I would again stress out the importance of interfaces of MTU 9000 and MTU 1500 not cohabiting in the same VLAN, and furthermore of not creating Jumbo frame VLANs connected to the Internet.

When dealing with VmWare, official VmWare documentation states you need VMXNET3 interfaces [and consequently open-vm-tools] for dealing with MTU=9000 Jumbo-enabled interfaces.

Jumbo frames also have to be configured in distributed vmware switches and in the VMWare Kernel before configuring them on the VMs. I think recently you are able to get away using them on ESxi. In the past they were only supported by the Enterprise VMWare licenses.

Check also Operation Jumbo Frames – MTU 9000 for VMware Networking

  • we test this case , from VM machine that configure MTU=9000 we copy some rpm file to other fysical machine , but we saw that on the fisical machine file size was zero ! , and when we unconfigure the VM and set MTU=1500 then copy the file to the fisical machine was ok and with the right chksum , so I am not sure where is the problem with the MTU or other? – yael Jun 24 '18 at 20:34
  • If tests did not go ok, and they are all in the same datacenter, I would check documentation whether the components involved (virtualization/version of hypervisor/VMWare / switches physical or virtual) support jumbo frames. Involve your suppliers if necessary. – Rui F Ribeiro Jun 24 '18 at 20:43
  • regarding my case do you think the problem is with the switches? – yael Jun 24 '18 at 20:47
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    you wrote - MTU=1900 ? instead of MTU=9000 – yael Jun 24 '18 at 21:08
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    so now the picture is more clearly , maybe because I not installed the open vmware tools on my VM I get the issue – yael Jun 24 '18 at 21:18

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