About a month ago I bought myself a fancy HP Procurve 1810G-24 from ebay to keep my NAS and ESX server company. Shortly before this, I decided to move my NAS and ESX whitebox to a rackmount solution. The switch and rack stuff arrived at almost the same time.
Obviously this was way too much for the IT nerd to handle so I dived into my rack transition right away, reinstalling my NAS with Ubuntu Server 12.04 and keeping its use restricted to SMB and NFS. Shortly after that, my ESX whitebox was unable to mount its NFS datastore. I checked and checked the NFS settings again and even reinstalled the ESX server (urgh, the pain of doing the Avamar VE install all over again was not something I was looking forward to). None of this did the trick. Vsphere simply refused to mount the NFS datastore, telling me that the NFS server was not reachable.
I even resorted to forwarding all traffic on the NAS and ESX ports to a laptop with wireshark to see where all these packets went. After looking into the logs, it seemed that there were sunrpc SYN packets coming from the ESX server, but they went nowhere.
Today, almost a month after the start of these issues, I decided to reinstall the NAS with Arch Linux again. I wasn’t to keen on the change to Ubuntu anyway so I went with it. To my surprise, I was again greeted by an ESX server refusing to mount the NFS datastore because it was unable to find the server.
Back to the drawing board, I decided to scrub google again, and after a few hours I found this remarkable small thread on the HP forums. A user reported issues with NFS once the auto-DOS function on his HP Procurve 1810g was enabled. Strange, I thought, but I can remember myself enabling and then disabling that function once. The issue seemed to be a bug in the latest P2.2 code for these switch types.
Since my issue had the same signature written all over it, I decided to hard reset the switch. 5 minutes later, my ESX server is happily accepting the NFS datastore.
Lesson learned I’d say. Sometimes the issue does not lie with the most obvious component but something stupid and small.