Now, for news I've got the advice to use NFS v2 because clients using v3 issue the readdir+ operation unique to v3 and this operation does some extra stuff (as opposed to v2's readdir) that most applications take advantage of but news software (INN nnrpd) has no use of the extra data returned by readdir+ and this makes it a performance loss to use v3 in this particular case.
Right. READDIR+ effectively does a stat() on each file that it returns, and that data is not used by the netnews software.
But... I've read that NFS writes are much faster in NFS v3 than v2. This, of course, leads me to my question (ta-daa) :
That's news to me, unless you're referring to the ability ot NFSv3 to use larger block sizes. For netnews, that's not likely to be of much benefit since most articles are very small.
- Are write operations slower on a NetApp server if you use NFS v2 compared to when you're using NFS v3? (and if so, about how much does it differ?)
Except for any block size effects, the performance should be nearly identical.
- (if the answer to the above question was 'yes') Could I leave the option "nfs.v3.enable" ON, on the NetApp and mount the filesystem from the reader clients using e.g "mount -o vers=2,proto=udp" (can't remember the exact syntax) while at the same time, from the client that is supposed to be doing a lot of *writing* to the NetApp, mount using version 3 to speed up the writes? This machine won't be running nnrpd so it won't be doing any readdir+ in vain.
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.