Re: /net support

[Ian Kent <raven@themaw.net>]

On Mon, 2006-10-30 at 19:14 -0500, David Meleedy wrote:
> 
> > My system defaults to tcp nfs v3 if no options are specified.  Given that
> > autofs now supports lazy mounts and unmounts, Is there a compelling reason
> > not to use TCP and/or version 3 mounts for the LAN?
> 
> 
> Well, my understanding of TCP is that it uses a sliding window/packet
> acknowledgment system to transfer data.  I would imagine that this
> would incur a bandwidth overhead vs. UDP.  So, given that it's more
> efficient to use UDP on the LAN, that is the behavior I had wanted to
> set up.

That very much depends on usage.

If you have a bunch of clients that typically open and load files of
potentially several hundred megabytes then UDP retransmits can become a
problem.

But then if traffic is light there's not much to be gained and if there
are traffic spikes possibly something to be lost.

> 
> > To answer your question directly, no, there isn't a way to specify mount
> > options per server.
> 
> I didn't think there would be at the moment.  Perhaps there would
> be a way to set this up with automounter variables, or some other
> mechanism.  I guess what I had been hoping for is that automounter
> could somehow detect how long it takes to contact a given server,
> and then depending on the lag, it would set the mount to be UDP
> for a short lag, or TCP version 3 for a long one.

This is actually fairly hard to do as ping responses can be so variable
for all sorts reasons. Not sure how to go about this one.

Ian