switch for channel bonding

Paul Nowoczynski pauln at psc.edu
Fri Aug 18 13:05:48 EDT 2000


i'm not disappointed at all!  it's great to hear that a switch
manufacturer got their act together and did a proper implementation..
i guess the BayNetworks 350-24T will be my next switch :)
paul

On Fri, 18 Aug 2000, Bogdan Costescu wrote:

> 
> On Fri, 18 Aug 2000, Paul Nowoczynski wrote:
> 
> > trunking, link aggregation, channel bonding, are all the same.  i think
> > the best method is to use 2 switches. the problem that i've seen on both
> > cisco and intel switches is that the recv streams are not divided between
> > the 2 recv'ing interfaces.  so don't expect to see ~180 mbits/sec
> > between a point-to-point sender/receiver application if you're using the
> > switch's trunking capability,  you'll need multiple streams to get that.
> 
> Sorry to dissapoint you, but I got this working. My BayNetworks 350-24T
> sends packets in the Round-Robin fashion and I was able to get more than
> 180 Mbit/s (measured with ttcp) with 2 3C905C cards in each node.
> One Cisco switch (that I have used but I don't administer) gave me at the
> beginning strange results. ifconfig would show for my 2 bonded NICs the
> same number of Tx packets, but very unbalanced Rx packets. Empirically (by
> looking at the LEDs on the back of the cards) I found that only one link
> was used normally and only if this link was busy, the second would be
> used. However, after I talked to the admin, I got "normal" results from
> ifconfig, showing very similar numbers for Rx packets; I haven't asked
> him again, but I guess that he changed something in the switch config (as
> the traffic didn't change). However, I'm not sure if this can change the
> bandwidth results.
> 
> > but if you can wire your cluster so that interface0 goes to one switch and
> > interface1 goes to another switch then you could get good point-to-point
> > bandwidth.
> 
> Using 2 different switches is one approach, but only solves one class of
> problems. For example, if you need 3 NICs/nodes, you need 3 switches and
> so on; the wiring might become problematic. On the other hand, there are
> applications which require only one node (let's call it master) to
> send/receive large amounts of data, while the computing nodes handle
> amounts of data which can "fit" into normal (single NIC) bandwidth. This
> problem can easily be solved by having a switch which supports
> channel-bonding/trunking/link-aggregation to which the master will be
> linked through bonded links, while the compute nodes will be able to use
> just 1 NIC. (and this applies just as well to a NFS server).
> 
> Sincerely,
> 
> Bogdan Costescu
> 
> IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
> Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
> Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
> E-mail: Bogdan.Costescu at IWR.Uni-Heidelberg.De
> 
> 


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