==> Regarding Re: [autofs] /net support; Ian Kent <[EMAIL PROTECTED]> adds:

raven> 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.

raven> That very much depends on usage.

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

raven> But then if traffic is light there's not much to be gained and if there
raven> 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.

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

Well, perhaps if the WAN is a different subnet we could reuse some of the
code from the replicated server support.  But you are right, ping times
are highly unreliable for making such decisions.

-Jeff

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