Conference 7.286::fddi

1421.0. "Shadow copy kills FDDI cluster" by GIDDAY::TAN () Thu Aug 11 1994 04:04

Hi, 
	A customer is complaining about an FDDI cluster using DEFTA-DA (DAS) 
cards.

	When he connects an AXP 3600 to a DB900MX, then to a Concentrator 900,
then to another bridge, then to another concentrator, and to another AXP 3600,
thence back to the first AXP3600 to complete the ring;  there is only an
ethernet connection between the two AXP, and no other Ethernet connections
on, to any of the two bridges.  Everything runs through the FDDI, (no DECnet
on SVA-0)  Both AXP runs V6.1, and the DEFTA-DA is at the current rev.

	He found that under normal circumstances, the FDDI cluster worked fine,
but if there is a shadow copy taking place, the shadow copy seemed to have 
taken the entire FDDI bandwidth, and his SCS traffic fell over to the ethernet.

	He claimed that if he removed the ethernet connection, the cluster would
hang, presumably SCS traffic cannot proceed on the FDDI.

	He has also tried with DEFTA-FA, (SAS) by connecting the AXPs to the
M ports on the Concentrators, and the two pairs of bridges and concentrator
forming a ring,  in this configuration, he can have the shadow copy taking 
place, and cluster would still be working fine.

	Both configurations appeared to be legal;  is it possible then, in the
DAS configuration, for a single shadow set copy to take up the entire FDDI band
width to such an extent that cluster traffic is excluded, resulting in cluster
hanging?  The SAS configuration appeared to be coping well!

	Would appreciate a prompt reply, thank you..

/Dave

Also entered in Cluster conference #4219
    

See CLUSTER conf #4216.1 & 4219.1.

BTW, why don't you wait a while before cross-posting and give folks a
chance to respond to the initial posting. otherwise we have to either
take time to chase the cross-posting or just ignore it and hope someone
else won't wast their time responding to something that's already been
solved...

'Gards, Verell