Weird NFS problems
jd at ugcs.caltech.edu
Fri May 27 15:47:16 PDT 2005
Oh, something else to try:
I checked through my notes and discovered that I had gotten UDP to work in
a similar configuration before. What I did was bind the IP address to
fxp0 instead of em0. By doing this, the kernel seems to send the data at
a pace suitable for the slow interface.
On Fri, 27 May 2005, Don Lewis wrote:
> On 26 May, Skylar Thompson wrote:
> > I'm having some problems with NFS serving on a FreeBSD 5.4-RELEASE
> > machine. The FreeBSD machine is the NFS/NIS server for a group of four
> > Linux clusters. The network archictecture looks like this:
> > 234/24 234/24
> > Cluster 1 --- |--------------- Cluster 3
> > | ---------------
> > em0| File server | fxp0
> > | --------------
> > Cluster 2 --- |--------------- Cluster 4
> > 234/24 230/24
> > em0 and fxp0 are bridged, and em0 has a 234/24 IP address while fxp0 is
> > just in promiscuous mode. 234/24 is an 802.1q VLAN on the fxp0 side of
> > the server, so packets are untagged at the switch just before fxp0, and
> > are forwarded to em0 through the bridge.
> > The problem manifests itself in large UDP NFS requests from Clusters 3
> > and 4. The export can be mounted fine from both those clusters, and
> > small transfers such as with ls work fine, but the moment any serious
> > data transfer starts, the entire mount just hangs. Running ethereal on
> > the file server shows a a lot of fragmented packets, and RPC
> > retransmissions on just a single request. Reducing the read and write
> > NFS buffers on the Linux clients to 1kB from the default of 4kB solves
> > the issue, but kills the transfer rate. The moment I go to 2kB, the
> > problem reappearss. Clusters 1 and 2 use the default of 4kB buffers, and
> > have no problems communicating to em0.
> > Poking through the list archives, I ran across this message
> > (http://lists.freebsd.org/pipermail/freebsd-stable/2003-May/001007.html)
> > that reveals a bug in the fxp(4) driver in 4-RELEASE that incorrectly
> > detects the capabilities of the NIC. Is this still an issue in
> > 5-RELEASE, or am I looking at a different problem? Any ideas on how I
> > can get the NFS buffers up to a reasonable level?
> That problem was fixed quite some time ago.
> Which transfer direction fails?
> Client writing to server
> Client reading from server
> Do you see all the fragments in the retransmitted request?
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