[Beowulf] automount on high ports
Bogdan.Costescu at iwr.uni-heidelberg.de
Wed Jul 2 10:12:09 EDT 2008
On Wed, 2 Jul 2008, Perry E. Metzger wrote:
> A given client would need to be forming over 1000 connections to a
> given server NFS port for that to be a problem.
Not quite. The reserved ports that are free for use (512 and up) are
not all free to be taken by NFS as it pleases - there are many daemons
that have to use those well-known ports. F.e. some years ago a common
complaint was that the CUPS daemon (port 631) was often conflicting
with NFS client mounts; I think that what was chosen by various
distributions was the easy way out - make the NFS client only allocate
ports starting at 650 or so.
> Every machine might get 1341 connections from clients, and every
> machine might make 1341 client connections going out to other
> machines None of this should cause you to run out of ports, period.
With all due respect, I think that you are not quite familiar with the
NFS implementation on Linux (and maybe other NFS implementations).
What you describe is the theoretical use of TCP connections; the way
NFS on Linux uses TCP is not quite as you imagine: there is one port
taken on the client for each NFS mount and that port is not reused.
Also mounting 2 different mount points from the same NFS server to the
same NFS client uses 2 TCP ports on the client side - at least with
NFS v2 and v3; for v4 I think that there is only one connection
between a client and a server independent on the number of mount
I do encourage you to subscribe to the Linux NFS list if you want to
learn more; I've been there for a long time (unfortunately not
anymore...) and the people, especially the developers, were very
IWR, University of Heidelberg, INF 368, D-69120 Heidelberg, Germany
Phone: +49 6221 54 8869/8240, Fax: +49 6221 54 8868/8850
E-mail: bogdan.costescu at iwr.uni-heidelberg.de
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