Unfortunately, it's the "feeder" machine (the one which is writing to the filer) that gets hit the hardest by using NFSv3. One operation that is hit particularly hard is renumbering the active file, though there are others that behave similarly.
But INND doesn't scan directories very much does it?
No, it doesn't, but other things that run on the same machine do.
Hmm, but I still haven't a clue about *what* programs generate the readdir+ requests? If not nnrpd and not innd, then what's left? On a newsfeed machine I run only those programs plus innfeed or possibly innxmit and I doubt that those scan directories a lot (or do they?).
Most people run expire and fastrm on their newsfeed machines. If you choose not to, we'll be happy to sell you more disk! :-) There's also expireover, and whatever other grot gets run from news.daily.
I was mistaken about the active file renumbering, though, which is part of innd and not a separate executable.
depends on how many users you have. Active file renumbering hammers at it continuously until it's done, so unless you have a pretty large number of users, I doubt nnrpd would account for "most" of the hit.
Hmm.... would it be possible to use two mount points for the same filesystem where one is mounted using NFS v2 and one using NFS v3 and then let ones own software choose whether to do an operation using v2 or v3 depending on what path it tries to open?
With active file renumbering being part of innd, no, not without some hacking on the code. Even for the separate executables, keeping the two straight might prove difficult. Why, though? For news, at least, NFS v3 has little, if any, benefit, and can badly hurt.
-- Karl