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Re: [Linux-cluster] Clusters with multihomed hosts



You can use bonding NICs with active-backup mode.

Only one NIC is used at a time, the second will only come up if the primary (active) fails.

Dont forget to configure miimon value for link monitor.

--

Flávio do Carmo Júnior aka waKKu

On Thu, Nov 13, 2008 at 2:21 PM, Michael O'Sullivan <michael osullivan auckland ac nz> wrote:
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

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