In my VMware vSphere home lab I have been using for shared storage various hardware or software appliances: from Openfiler, Falconstor VSA, HP LeftHand/StorageWorks P4000 VSA to EMC Celerra VSA. Recently I have added Iomega ix4-200d. Its NFS sharing is VMware vSphere certified. Although Iomega is not very powerfull (see my previous blog post about Iomega) I moved all my VMs to it to free up my storage server to play with other storage appliances (I am testing Nexenta now, but that is for another blog post).
My setup is now very simple. I have diskless ESXi that runs all the VMs from the NFS datastore served by Iomega. Today I have restarted the ESXi server and was surprised that due to inaccessible NFS datastore no VM was started. The datastore was grayed out in the vSphere Client GUI.
I have virtual domain controller, internet firewall/router, mail server and some other less important machines. So if the ESX does not start properly I have no internet, email and I cannot even log in to Iomega CIFS shares because it is joined to domain which was also not available.
I was very surprised as I had no idea why the ESX server could not connect to the NFS datastore. Storege rescan did not help, so I have unmounted the datastore and tried to reconnect it. I received this error message:
Call “HostDatastoreSystem.CreateNasDatastore” for object “ha-datastoresystem” on ESXi “10.0.4.202” failed.
Operation failed, diagnostics report: Unable to complete Sysinfo operation. Please see the VMkernel log file for more details.
VMkernel log (which is on ESXi stored in /var/log/messages) did not help much:
Jan 15 22:10:25 vmkernel: 0:00:01:30.282 cpu0:4767)WARNING: NFS: 946: MOUNT RPC failed with RPC status 13 (RPC was aborted due to timeout) trying to mount Server (10.0.4.251) Path (/nfs/Iomega)
I was able to connect to the NFS Iomega export from regular linux machine. I was also able to connect the ESX server to regular linux NFS export. And that helped me to find the solution.
Because both of my DNS servers were running in virtual machines and not accessible, Iomega took more time to connect the ESX server to the NFS datastore and ESX server meanwhile gave up. The remedy was very simple. To Iomega /etc/hosts file I have added a line with the ESX server IP address and its hostname. This must be done via Iomega ssh console and not via web GUI:
root@Iomega:/# cat /etc/hosts
127.0.0.1 localhost.localdomain localhost
10.0.4.251 Iomega.FOJTA.COM Iomega
10.0.2.251 Iomega.FOJTA.COM Iomega
10.0.4.202 esx2.fojta.com esx2
From now when the ESX server reboots it mounts the NFS datastore immediately.
Tom Fojta's Blog 
I was ripping my hair out trying to find out why I could not see my nfs mount until I saw your blog. Thank you kind sir
hi
check the NFS service is running or not in Serever itself