On Wed, Feb 20, 2019 at 11:28:53AM +0000, James Pearson wrote: > On a very busy NFSv3 server (running CentOS 6), we recently upped the > nfsd thread count to 1024 - but this caused client mount requests over > UDP to fail. > > We configure all our clients to use TCP for NFS mounts, but the > automounter (automountd) on MacOS (up to version MacOS 10.12) seeds a > 'null call' to the NFS server over UDP before attempting the mount - > but the server appears to ignore any UDP requests - and the automount > fails By the way, you might also just turn off UDP. (Start run rpc.nfsd with the -U option.) Hopefully MacOS can handle that case. --b. > > I can also reproduce the issue on a Linux client via: > > mount -o udp,nfsvers=3 server:/export /mount/point > > I've found, by trial and error, that the maximum number of nfsd > threads that can be run on the server is 1017 before UDP mount > requests fail > > Running tcpdump on the server shows the UDP requests from the client, > but the server never replies > > It looks like more recent versions of MacOS will do its test 'null > call' over TCP - so that is one 'solution' to this issue > > However, I'm interested to know if we're hitting some hard limit, or > if there are any settings we can tweak that could mitigate the > problem? > > Thanks > > James Pearson
