Conference 7.286::fddi

None that I know of.  There isn't enough room on a (single width) card for
two FDDI ports.

On the other hand, you can put in multiple adapters if you want, that gives
you everything a DAS does and a lot more.

	paul

    You've got to watch out which hardware platform and which turbo channel
    is on that platform. One I know of (on a VAX 4000-60) can only have one
    turbo channel option card plugged in,.. so multiple adapters
    	would not be an option there...
    
    						/Bill
    

I'm ofcourse curious to hear WHY you think you want DAS connection for
any user equipment, please add that as replies to this note, BUT

For anybody who asks for DAS connection for a workstation or any other
user controlled equipment I have to ask;

	Have you throught about what happens to your dual ring when
	that user powers off his workstation ?

If I'm correct - the RING WILL WRAP ! since there is a "break" in it.

OK - No now somebody at the other end of the campus powers off his
DAS workstation. WHAT HAPPENS ? The ring will WRAP again !

	YOU NOW HAVE TWO RINGS !!! your other users have now lost connectivity!!
	ANd that was not created by any technical fault, only carlessness.

The Dual FDDI ring is only designed to cope well with one break. That is
ofcourse better than any other common LAN technology, but still not enough
if we introduce too many end user systems on the Dual Ring.

What I'm saying is that directly on the dual ring you only want to connect 
equipment that you can lock away and hide from the normal user. Equipment
that STAYS powered on and ensures the integrity of the ring.

 OK - I hear someone Saying " But I use Optical Bypass Relays on all stations"

Well - if you have them on all stations there will be extra optical losses
in each extra connector and there is no way to ensure that the configuration
is "leagal" when X workstations have powered of. See more in the Jan -92 
Supplement to the Networks Buyers Guide.

The best way to increase nework connectivity for end user equipement is 
dual controllers connected to two different concentrators.

Torbjorn

Hang on a bit...

This topic has been discussed, or confused, before.  You're saying you're
arguing against DAS user stations.  But the arguments have nothing to do
with that -- they have to do with the problems of connecting user stations
DIRECTLY to the dual ring.

There is NO problem with connecting DAS stations to concentrators; that
is every bit as good (and with dual homing, somewhat better) than connecting
a SAS to a concentrator.

This is an important point to get right.  Customers often ask for DAS, and
get upset if we tell them that's a bad idea.  The right answer is to tell
them what we have and don't have (note that we have DAS in a bunch of
places, e.g., bridges) and also to go over the benefits of using concentrators.
Explaining the problems of connecting directly to the dual ring is a good
idea, but make sure it does NOT come across as an attack on DAS in general.

	paul

Paul,

I stand corrected.

I only adressed part of the problem... 

I agree that DAS interface dual homed is goodness, and you do not seem to
disagree when I say that end user equipment on the dual ring is not.

But as I think you have said in other discussions TWO SAS cards and good
software support can bring even more than a Dual-Homed DAS card.

the $10000 question is now obvious - Do Digital provide good software
support, failover etc..., for two (or more) SAS cards in one system ? 

TL

    and the answer to the $10000 question is:
    
    	" It depends "
    
    
    It all depends on what software you are talking about. All VMS
    supplies really is a driver for the device. The driver can (and
    does) signal hardware failures to the "next layer up". But the
    action taken (failing over) must be taken by "the next layer up"
    
    In the case of clusters, the next layer up is PEDRIVER, and as of
    V5.4-3 PEDRIVER is very good at doing the failover.
    
    In the case of LAT/DECnet/you name it you have to find out
    what each product does. So the question becomes which
    products does the customer need with auto-failover? When
    you have that list,. you really have to go to each product
    and find out what the capabilities are.
    
    Hope this helps
    
    							/Bill