topic Re: Cluster communication in Operating System - OpenVMS

Cluster communication

joukj — Mon, 08 Oct 2018 08:48:14 GMT

Hi all,

On my alpha cluster with only one network device per machine I always see my satellites going down when the network fails (logical beacause they need the system disk from the boot member).

How does this work with 2 network devices?

The reason for asking is that on one of the networks there will be maintanance (replacing the switches).

The machines in theis networks are Itanium machines running OpenVMs8.4. Both have two network interfaces both connected to a network. The satallites are booted using the network of interface A. The network on interface A will be down during the replacement of the switches, while the network on interface B will continue to work. Does interface B take over the cluster communication, so that I can keep the satallites running while the network on interface A is down?

Re: Cluster communication

Volker Halle — Mon, 08 Oct 2018 09:15:20 GMT

Cluster communication dynamically uses all avaiable 'channels', i.e. LAN interface endpoints between all systems in a cluster.

$ MC SCACP SHOW CHANNEL will show all available channels from each node to all other nodes in the cluster. As long as at least one channel is available (Open) from each node to ALL other nodes, cluster communication will continue to work.

Volker.

Re: Cluster communication

joukj — Mon, 08 Oct 2018 09:39:47 GMT

Looks like only one interface is used.. The second network was added after building the cluster. Should I start communication mannually with MC SCACP START LAN EWB on all machines?

Re: Cluster communication

joukj — Mon, 08 Oct 2018 10:13:36 GMT

However If I give

MC SCACP SHOW LAN

I see both interfaces and both have the status ""Run Online Restart"

Why are they not showing up both in the Chann el list?

Re: Cluster communication

Volker Halle — Mon, 08 Oct 2018 15:28:14 GMT

If the LAN interfaces show up as 'run' on SCACP> SHOW LAN, but the secondary (new network) LAN interfaces do not show up on SCACP> SHOW CHANNEL; chances are high, that those network interfaces are NOT connected correctly to each other ! Do the packet counters increase on the secondary LAN interfaces ?

Cluster communication determines reachability using cluster multicast messages on all connected LAN interfaces and dynamically adds new channels.

Volker.

Re: Cluster communication

joukj — Tue, 09 Oct 2018 07:47:24 GMT

You are probably right: I think my university blocked something on this network. I'm trying to figure out if they can "unblock" it during the replacement. of the switches.