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Re: [Linux-cluster] Private Network for all cluster comms?



On 11/19/2010 02:46 PM, Colin Simpson wrote:
I'm looking at implementing a RHEL 6 based cluster using DRBD. For this
I plan to have a dedicated fast bonded network between the two nodes for
the backend DRBD Storage Network (SN), well a 10Gb with a 1Gb failover.

A good plan

Most examples I've seen of doing this seem to use the SN as ringnumber 1
in totem, does it make more sense to be ringnumber 0. I assume this
could be accomplished by setting the hostnames associated with SN
network IPs as the node names in cluster.conf. And put the altname in as
the hostname associated with the main network IPs.

I don't think it matters much, assuming that your cluster communication is also on a private network. I'd sort of argue that the cluster comm network would be quieter and thus less likely to suffer latency which you might see during periods of high disk I/O on your storage network.

My reasons for thinking of doing this are that my SN network will be
back to back wired so more reliable than a switch based network but more
importantly it's performance will be higher for GFS2 locking etc

For this reason, it is a good one to use, regardless of whether it is ring 0 or 1.

Does this make sense to do (anyone else do this)?

I do this.

Does this make management harder at all say from a central off cluster
luci, that the node names are not themselves are not resolveable from
the main network DNS (the altname's will be). Any other nastyness that
might arise?

When a ring fails, for any reason, it's recovery must be performed manually.

One thing I don't like is the machine hostnames will not be their
network DNS names. Would the cluster suite be happy if the hostname of
the node matches the "altname" but not the "clusternode name"?

Cluster comm will, iirc, happen on the network resolved by `uname -n`. I'm not certain of this though, as it may be tied to the interface of the active ring.

As a quick aside, I've only played with clustering on RHEL5 before so on
RHEL6 does corosync.conf get generated from cluster.conf. If not, what
would happen if I hand craft a corosync.conf for doing my config above ?

In RHCS3, corosync.conf should not, and is not used. Everything comes from cluster.conf.

Would this upset things with regards using keeping things the right way
around in cluster.conf with regards "clusternode name" and "altname"?

My only real concern is that your SN could get too noisy. Personally, I'd advice making it ring 0 and leaving your names alone. That said, either *should* work.

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