make the experimental NFS subsystem the default one

[Chris Forgeron]

I use the NFS server in FreeBSD 9.0 pretty heavily. I drive a VMware ESX cluster off three FreeBSD 9.0-Current boxes using ZFS v28 (Yeah, I know, a bit risky, but it's more stable than OpenSolaris under my environment). 

While I'm a bit hesitant about any changes to what is working fairly well for me, I agree that we'll never move forward unless this is the default so it will receive more testing. 

With no plans from VMware for NFS 4.x in the near future, I'd say that NFS v3 will continue to be very important to the VMware crowd in FreeBSD for some time. 

I've hacked up the old NFS server a bit to better serve my ESX/NFS needs (forcing it to always write async so it works faster with ZFS and a ZIL). I guess I could do the same to the new code as well...

..However, if you didn't mind adding switch to force the NFS server to quietly only do an async VOP_WRITE, that would be really handy. Very dangerous for some people, but then again, so are most switches if you don't understand what they do.  ESX will only opens it's files with O_SYNC, and it's not an editable option, so people like me running ESX+NFS over a ZFS share that has a ZIL are making the system do a lot of unnecessary sync writes. Yes, I know about SSD/RAM for the ZIL, but it still slows it down quite a bit over an async write.