On Wed, 27 Apr 2005, amalgamatedsystems wrote:
> We had a similar problem between our linux server (running on a PC)
> and a TS-7200. Anyway, any large file activity would "hang" the NFS.
> As NFS is UDP/IP and not TCP/IP our problem was that we had the
> TS-7200 board on a 10Mbit hub, while our PC was connected to a 100Mbit
> switch (10Mbit unlink between). Because there is not flow control
> with UDP/IP the 100Mbit would choke the 10Mbit. If we connected
> either node to the same switch and/or hub the problem went away.
> Whether it was a flow control problem or not I could not fully
> conculude without some serious debugging.
I think the problem is to do with IP fragmentation. When sending frames
larger than the network MTU (1500 less UDP/RPC headers bytes) the frame is
Fragmented, i.e. sent over 2 or more IP packets. If you have a speed
mismatch and bad buffering then you can get consistant loss of 2nd/3rd/4th
fragment packets. When its retransmitted you get the same loss. In such
cases the best thing to do is to lower wsize and rsize options to a value
that means there is no fragmentation. I can't remember the overheads, but
a figure of 1420 for r/wsize rings a bell for standard ethernet. Though
I've seen some recommendations of 1024.
If supported NFS over TCP doesn't suffer these problems and is more
resilient in congested networks.
>
> Regards,
>
> Clive
>
>
> --- In "vocemanago" <> wrote:
> >
> > I have a question about the network mounting piece of linux. Is there
> > some kind of direct limitation (due to driver or something) that
> > doesn't allow more than one NFS mount on this board?
> > Also is there a throughput issue when using NFS that I should address
> > before doing things like a "kernel build" in the NFS mount?
> >
> > I have a debian linux server now, which is offering up the /home
> > directory to the development debian environment on the TS-7200. It
> > connects ok and navigation isn't a problem, but when I do something
> > disk intensive, it locks up the operation fairly hard. Is there some
> > kind of "open files" limitation perhaps? Where you can't open more
> > than two (or one) file at a time on the NFS mount?
> >
> > The whole telnet console is stuck, I have to log in under another
> > telnet client and kill the whole situation from there.
> >
> > Doing something like a make in the NFS seems to cause it. I think I
> > had problems moving large files or sets of directories.
> > Anyone have a clue.
> >
> > Obviously there are all kinds of configuratoin issues, but I was
> > curious if there are any linux gurus out there who know the "magic"
> > arrangement that pretty much always works.
> >
> > Interestingly I have an old NAS device (an old Snap server) which can
> > be anything under the sun as far as disk linkage goes (windows share,
> > netware driver,apple talk drive,NFS , www server)... and it appears
> > quite capable of take an NFS mount and doesn't seem to bother the
> > TS-7200 much at all. I expect internally it is some kind of linux or
> > BSD kernel.
> >
> > I wonder if it has to do with the difference between synch and asynch
> > file mainpulation.
> >
> > Tony
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
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