[gpfsug-discuss] mmchconfig subnets

[Eric Horst]

Hi, I'm hoping somebody has insights into how the subnets option actually
works. I've read the docs a dozen times and I want to make sure I
understand before I take my production cluster down to make the changes.

On the current cluster the daemon addresses are on a gpfs private network
and the admin addresses are on a public network. I'm changing so both
daemon and admin are public and the subnets option is used to utilize the
private network. This is to facilitate remote mounts to an independent
cluster.

The confusing factor in my case, not covered in the docs, is that the gpfs
private network is subnetted and static routes are used to reach them. That
is, there are three private networks, one for each datacenter and the
cluster nodes daemon interfaces are spread between the three.

172.16.141.32/27
172.16.141.24/29
172.16.141.128/27

A router connects these three networks but are otherwise 100% private.

For my mmchconfig subnets command should I use this?

mmchconfig subnets="172.16.141.24 172.16.141.32 172.16.141.128"

Where I get confused is that I'm trying to reason through how Spectrum
Scale is utilizing the subnets setting to decide if this will have the
desired result on my cluster. If I change the node addresses to their
public addresses, ie the private addresses are not explicitly configured in
Scale, then how are the private addresses discovered? Does each node use
the subnets option to identify that it has a private address and then
dynamically shares that with the cluster?

Thanks in advance for your clarifying comments.

-Eric

--

Eric Horst
University of Washington
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