[Linux-cluster] Clusters with multihomed hosts

[Michael O'Sullivan]

Hi all,

I need to know more about using redundant NICs in clusters.

I have a 2-node cluster with 2 NICs in each node. The first NICs on each 
node are connected to one switch, the second NICs on each node are 
connected to another switch. This is an experimental arrangement so I am 
using /etc/hosts instead of DNS. It appears that the cluster software 
becomes confused if I put both NICs for the hosts in the /etc/hosts 
file, even if they are in different subnets. Here is the /etc/hosts file 
I would like to use:

# localhost line
192.168.10.1     node1
192.168.10.2     node2
192.168.20.1     node1 # Second NIC on node 1
192.168.20.2     node2 # Second NIC on node 2

but this seems to cause the cluster to hang (confused about which NIC to 
use?), so I have removed the last 2 lines and everything works fine. 
However, this means if the switch on the 192.168.10.x subnet fails the 
cluster will "break". If the cluster would recognise that node1 and 
node2 are available via the second NICs then I wouldn't have to worry 
about this single point-of-failure.

I have thought about bonding the NICs which (I think) would take care of 
the problem, but I have heard that boding two NICs usually does not  
give double the bandwidth. I  have read a little about high-availability 
and failing over IP addresses, but this seems to be between different 
nodes, not different NICs in the same host.

Would anyone please be able to give me some direction about the best way 
to set up my cluster and NICs to make the cluster reliable in the event 
of switch failure? And keep the full bandwidth of the NICs intact?

Thanks in advance for any help you can give. Kind regards, Mike