I ran across an unusual situation recently. We have a customer who uses an Iomega ix12-300r NAS unit to provide NFS storage to their vSphere 4.1 ESXi hosts. The NAS device hung, taking down the virtual environment. It responded to a ping, but would not display the html management console.

A hard reboot resolved the issue with the management console and we could log into the device, but it was still not serving NFS. It took a lot of troubleshooting before we realized the DNS server specified in the ix12-300r network settings was one of the virtual machines that was offline. We cleared the DNS field and saved the settings and the NFS shares appeared on the ESXi hosts immediately, and we were able to power on the virtual machines. It appears that if a DNS server is specified on the network settings page it must be accessible for NFS to function.

It's interesting to note that we used IP addresses on both the ESXi hosts and the ix12-300r, not host names, and that NFS works fine with the DNS field blank.