Hello. I'm simply posting this here because in tackling my own VTL/FC/NB status 84 problem, I never did see anything that really pointed me toward the solution specific to my install. Probably because it's so elementary.
By posting this, I'm making myself look like an utter idiot. If I can save someone else a headache, I'm ok with that.
We saw occasional status 84 errors when our VTL was under moderate loads; it would run fine at light loads.
After a long period of wrestling with this problem on the software side of things - tweaking our HBA settings, trying different HBA driver revs, etc. - I finally decided to take a physical look at things.
That's when I discovered that the installers had used single-mode fiber in the fiber runs from our (NetApp) VTL to the FC switch. Mysteriously, they had used (correctly) multi-mode from the switch to the servers and from the switch to our physical tape silo.
Moral of the story: Start with the easy stuff. Check the physical connections and components first. Save yourself many nights of headaches assuming that it was done correctly.
