Re: NFS writes and ZFS

On Wednesday 23 July 2008, Bernd Walter wrote:
> On Wed, Jul 23, 2008 at 10:24:01AM +0200, Pawel Jakub Dawidek wrote:
> > On Tue, Jul 22, 2008 at 11:28:27AM -0400, John Nielsen wrote:
> > > I have a FreeBSD server (which I use as a NAS device, among other
> > > things) and a FreeBSD deskop. The desktop is running 7-STABLE from a
> > > couple days ago and the server is running 8-CURRENT from yesterday.
> > > The server has several NFS-exported ZFS'es which I mount from the
> > > desktop. Since moving the shares to ZFS I've been having trouble
> > > writing to them from the desktop--the mount hangs after the first or
> > > second attempt. This is similar if not identical to what's described
> > > in the thread
> > > (from -current) I partially copied below.
> > >
> > > Today I discovered that the problem seems to go away if I change the
> > > NFS mount options on the desktop. The following is a summary/timeline
> > > of what I've tried:
> > >
> > > 7-STABLE client, no NFS options (defaults); 7-STABLE server, UFS;
> > > works 7-STABLE client, no NFS options (defaults); 7-STABLE server,
> > > ZFS; broken 7-STABLE client, no NFS options (defaults); 8-CURRENT
> > > server, ZFS; broken 7-STABLE client, tcp,nfsv3,-r32768,-w32768;
> > > 8-CURRENT server, ZFS, works
> >
> > Do you need all the options here? If not, could you try to find the
> > smallest subset of options that are needed to make ZFS work? Maybe
> > 'nfsv3' is all that is needed, or 'tcp' alone fixes it? At work we use
> > many NFS exported ZFS file systems, mostly accessed from MacOS X and
> > we see no problems.
>
> Whenever changing NFS transport options has an influence on reliability
> my first task is to verify the network.
> Especially there were often hardware problems with some NIC lately,
> of which some have worked around in the drivers and some not.
> Disabling TSO and checksum offloading typically helps.
> This kind of problem is typical on both the client and server, but also
> on routers.
> Of course network problems can also be on any cable, switch in between
> as well, but are less typical to produce complete NFS hangs.

A good strategy I'm sure. However in this case the whole network is within 
arm's reach, the switch and cables are brand new and I haven't had any 
other issues that would point to a network fault. Further, I saw the exact 
same behavior on a completely different set of hardware around the time of 
7-BETA. In both cases the NFS shares worked fine prior to my moving the 
shared ports tree to ZFS.

PJD- I'll try to narrow the options needed this afternoon or tomorrow and 
let you know what I find.

JN