Conference 7.286::fddi

1420.0. "DEFTA-DA and FDDI cluster" by GIDDAY::STANISLAUS () Wed Aug 10 1994 12:06

    
    
    	We have a customer with two DEC3000-600 (alpha systems) and two
    DECconcentrator 900 units and two DECbridge 900 units in an FDDI ring.
    The DEC3000-600 uses the DAS FDDI controllers called DEFTA-DA in both
    systems. The two Alpha systems are interconnected by Ethernet. This
    Ethernet does not connect anything else.
    
    	Customer is running DECnet only on FDDI circuits of Alpha.
    
    	SCA runs on both (FDDI and Ethernet) circuits.
                              
    	Customer starts a shadow copy operation on the Alpha to shadow copy
    a disk on one Alpha system to a disk on the other Alpha syste. Shadow
    copy takes place across the FDDI. AT this point all other SCA traffic
    starts using the Ethernet as the primary path. Why ? I am not sure, but
    may be because it finds Ethernet to be faster than FDDI when shadow
    copy commences using FDDI. At this point if the customer unplugs the 
    Ethernet from one of the ALpha systems, the cluster consisting of the
    two Alpha systems running OpenVMS hangs.
    
    	Customer changed above configuration as follows:
    
    	Removed the DEFTA-DA (DAS) and replaced with DEFTA-FA (SAS) boards
    on both DEC3000-600 systems. Connected the two DECbridge 900 units and
    two DECconcentrator 900 units in an FDDI ring. Connected one ALpha to
    one DEcconcentrator's M port and the other Alpha to the other
    DEcconcentrator 900. Then starts shadow copy on FDDI as before. Then he
    unplugs the Ethernet cable from one of the ALpha systems and everything
    works fine. The cluster made-up of the two ALpha Systems does not hang.
    
    	So it appears that the DEFTA-DA has some problem. But I think in
    the second config the Alpha systems have a 200 Mbs FDX connection
    whereas in the first configuration the Alpha systems are in a 100 Mbs
    FDDI ring. Could that be the reaon for the problem.
    
    Alphonse

No, they aren't operating fdx; they must either be connected point to point
or to a switch.

And no, you can not use the defta-da without new vms drivers; the reason that
the traffic was running of ethernet is becuase that's the only working path.