[Info-vax] hub better than switch?!

[Jan-Erik Soderholm]

Bob Gezelter wrote 2012-03-04 12:11:
> On Sunday, March 4, 2012 2:14:31 AM UTC-5, Phillip Helbig---undress to
> reply wrote:
>> A while back, I posted a question about a slowly (about 2 per day)
>> increasing error count, mostly on PEA0: but occasionally on some
>> disks connected to the same machine which shows the errors on PEA0:.
>> This stopped after my old switch died and I replaced it with a hub
>> (actually this strange 10/100 Mb/s hybrid thingamajig).  I assumed
>> that whatever caused the switch to fail was also responsible for these
>> errors before the failure.
>>
>> Since I replaced this "hub" with a brand new 10/100/1000 MB/s proper
>> switch a few days ago, the increasing error count is back.  :-(  It
>> occurs on the one machine in the cluster which has a 100 MB/s
>> ethernet card (the others have 10).  On the switch, this is running at
>> 100 while on the "hub" it ran at 10 (but other things on the hub---an
>> access point and another switch---ran at 100).
>
> Phillip,
>
> Two possibilities occur to me: - Possible problem with the switch
> hardware - Duplex mismatch problems
>
> I have seen strange results when a machine/switch disagree on duplex.
> The underlying problem (squelched/lost messages or parts thereof) are
> clear, but the precise times when they occur can be difficult to
> predict.
>
> I would also be concerned about a loose connection "jittering" due to
> vibration. Most likely this would involve the modular cable from the VMS
> system, but I have seen situations where the power connector for the
> switch was at fault.
>
> Careful trouble shooting will resolve the problem, although it is
> excruciating with a failure event frequency of 2/day.
>
> - Bob Gezelter, http://www.rlgsc.com

I had a similar problem with a DS25 and a D-Link DES-1016D (unmanaged
16-port 10/100 switch).

I had the DS25 set hard to 100FD but the auto negotiation in the D-Link
failed to "see" this and defaulted to some single duplex mode. When
I changed the DS25 to "auto" everything worked fine.

Now, I do not think this is some simple duplex problem, that usualy
created *big* problems when FTP'ing. One direction usualy works fine,
the other direction usualy hangs for any files larger then
a few disk blocks (I guess/hope that is tested).

Anyway, the specific errors from the device mentioned would be fine.

Jan-Erik.