NFS Question

[Hewitt Tech]

Be very careful in how you choose to mount your NFS filesystem. Hard
mounting is usually the default for most implementations for a good reason.
If you are writing to a file on a hard mounted NFS filesystem, if the
connection between client and server is lost, NFS will wait until the server
becomes available and then completes the I/O operation. This is why the
client process appears to be hung under these circumstances. If on the othe
hand you choose to 'soft mount' your NFS filesystem, if the path is lost or
there are a number of timeouts (typically 5), the I/O operation will be
failed and an error status returned to the client. Unfortunately many user
programs don't check the I/O status and you might be left wondering why your
data never got to the file. Soft mounting is mostly appropriate for the
situation where file access is read only and you want to be able to allow
the client process to be stopped should either a network or server outage
occurs.

-Alex

----- Original Message -----
From: "Rich Payne" <rdp at talisman.mv.com>
To: "Kenneth E. Lussier" <ken.lussier at zuken.com>
Cc: <discuss at gnhlug.org>
Sent: Thursday, August 29, 2002 3:43 PM
Subject: Re: NFS Question


> On 29 Aug 2002, Kenneth E. Lussier wrote:
>
> > Hi All,
> >
> > I have a couple of (simple) questions about NFS, and I'm sure someone
> > here can smack me with a clue-stick...
> >
> > 1) If applications are mounted via NFS, and someone runs the
> > application, is the processor on the NFS server or the client system
> > used? (I'm pretty sure it's the client, but I was told different today,
> > so now I'm not sure..)
>
> The client's processor is used to run the app. The server's processor is
> only used in terms of sending the files. So, there's no need for the archs
> of the two machines to be the same (as an exmaple I have a Sparc at home
> with my MP3s on it and play the MP3s from an Alpha).
>
> > 2) What sort of problems are there with NFS on Linux? I have heard that
> > there are file locking problems, but nothing really in depth. Anyone
> > care to elaborate?
>
> NFS in general tends to be very sensitive to hicups and delays in the
> network. One thing to keep in mind is that if you have 'hard' mounts and
> the NFS server goes away, the client will hang.
>
> At work we have many Linux systems mounting most of their filesystems from
> a Network Appliance server and most of the time there's no trouble.
> Linux's NFS (client) side has come along way as is quite reliable these
> days. I can't speak for the server side (under any serious load), though
> I've heard it has improved.
>
> --rdp
>
> --
> Rich Payne
> http://talisman.mv.com
>
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