Re: Massive NFS problems on large cluster with large number of mounts

[Trond Myklebust <trond.myklebust@fys.uio.no>]

On Wed, 2008-07-02 at 16:31 -0400, J. Bruce Fields wrote:
> On Wed, Jul 02, 2008 at 04:00:21PM +0200, Carsten Aulbert wrote:
> > Hi all,
> > 
> > 
> > J. Bruce Fields wrote:
> > > 
> > > I'm slightly confused--the above is all about server configuration, but
> > > the below seems to describe only client problems?
> > 
> > Well, yes and no. All our servers are clients as well. I.e. we have
> > ~1340 nodes which all export a local directory to be cross-mounted.
> > 
> > >> (1) All our mounts use nfsvers=3 why is rpc.idmapd involved at all?
> > > 
> > > Are there actually files named "idmap" in those directories?  (Looks to
> > > me like they're only created in the v4 case, so I assume those open
> > > calls would return ENOENT if they didn't return ENFILE....)
> > 
> > No there is not and since we are not running v4 yet, we've disabled the
> > start for these on all nodes now.
> > 
> > 
> > > 
> > >> (2) Why is this daemon growing so extremely large?
> > >> # ps aux|grep rpc.idmapd
> > >> root      2309  0.1 16.2 2037152 1326944 ?     Ss   Jun30   1:24
> > >> /usr/sbin/rpc.idmapd
> > > 
> > > I think rpc.idmapd has some state for each directory whether they're for
> > > a v4 client or not, since it's using dnotify to watch for an "idmap"
> > > file to appear in each one.  The above shows about 2k per mount?
> > 
> > As you have written in your other email, yes that's 2 GByte and I've
> > seen boxes where > 500 mounts hung that the process was using all of the
> > 8 GByte. So I do think there is a bug.
> > 
> > OTOH, we still have the problem, that we can only mount up to ~ 350
> > remote directories. This one we think we tracked down to the fact that
> > the NFS clients refuse to use ports >1023 even though the servers are
> > exporting with the "insecure" option. Is there a way to force this?
> > Right now the NFS clients use ports 665-1023 (except a few odd ports
> > which were in use earlier).
> > 
> > Any hint for us how we shall proceed and maybe force the clients to also
> > use ports > 1023? I think that would solve our problems.
> 
> I think the below (untested) would tell the client to stop demanding a
> privileged port.

Alternatively, just change the values of /proc/sys/sunrpc/min_resvport
and /proc/sys/sunrpc/max_resvport to whatever range of ports you
actually want to use.

Trond