Has anyone got tcp enabled? Have they seen any problems/benefits, or are there any known issues with this?
...
still are some UNIX clients around whose NFS v3 implementations leave something to be desired on the stability and performance fronts. Hence the default disablement of some of the fancier combinations, to prevent them from being selected by accident.
The question was about TCP, not the version of the NFS protocol. The defaults for 5.2 are
options nfs.tcp.enable off options nfs.v3.enable on
The reason for that choice had nothing to do with stability nor with any client issues so far as I know, but rather because most customers see a performance hit when running TCP with enabled, and having the low-performance option being the default didn't make a lot of sense.
Most customers see the hit because they're running over a LAN. In a WAN environment, NFS-over-TCP is great because it does a much better job of dealing with slow and possibly lossy networks, but over a LAN it simply adds overhead to deal with non-existant problems. The hit seems to be about 10-20% based on SPEC SFS results -- see
http://www.netapp.com/products/spec/spec2.html
Note that comparing UDP and TCP SFS results is meaningful (with the same protocol version, hardware, and testbed), but comparing V2 and V3 results is NOT meaningful because the workloads are different.
-- Karl