Posted on

vmware – lost connection to nfs datastore

In your vmware environment you have created a nfs datastore but when you are trying to copy files to it, you lost the connection.


You can check the file vmkernel.log that you can find in your esx host in :


You should find these lines of error :

Lost connection to the server mount point /yourdatastorefolder mounted as ........... ("yourdatastorename")

Restored connection to the server mount point /yourdatastorefolder mounted as ........... ("yourdatastorename")


vmnic3: 4026 bytes packet couldn't be sent (mtu=1500)


vmnic3: oversized tsoMss: 8948, mtu=1500


As explained in vmware documentation you have to check communication with your nfs datastore. So using , for example Putty over ssh, you can :

Ping your nfs datastore


Find your vmkernel network card :

esxcfg-vmknic -l

In the output you can see the MTU value of your network card and which is the vmkernel network card. Now you can ping your datastore using the network card, trying different MTU values :

vmkping -I vmk1 -s 1420

You probably need to change the MTU of your esx host’s network card. Maybe you have an MTU set to 9000 and you need to set it to 1500.

Using the vsphere client : Configuration – Networking. Select vmkernel network card and select “Properties” . Select “Vmkernel” and click on “Edit” :

Change MTU:

You will be able to see the new MTU value using the previou command :

esxcfg-vmknic -l