[Linux-cluster] Can i use 2 nodes from a cluster?

Michael Schwartzkopff misch at schwartzkopff.org
Tue Oct 22 20:46:28 UTC 2013

Am Dienstag, 22. Oktober 2013, 22:21:02 schrieb C. Handel:
> place a loadbalancer in front of the cluster. Buy hardware, for example F5
> or coyote. Or go for software with haproxy and keepalived.

Use ldirectord and pacemaker. Trust me.

> The software
> loadbalancer is a shared nothing. You only need to keep the config in sync
> (for example using csync2). Configure load balancing with sticky sessions
> based on incoming ips.

You might want to sync the stored connections. ipvs has a demon, that takes 
care of this.

> Create a redhat cluster with four nodes. Main service provided by rhcs is
> GFS2. This allows you to share configfiles and web delivery files the same
> on all nodes.

Not needed to set up a full blown RH cluster. Keep the config files in sync 
with a simple rsync or csync. No further shared storage needed. Just use 
corosync for the cluster communication and pacemaker for the resource 
management. Resources are the ldirectord and the virtual IP.

> Start an apache on each node (via clones).

Or start it separate on every node via init  or systenmd. no cluster needed in 
the backend web servers.

> Traffic goes through loadbalancer and hits all rhcs nodes. Bandwith limit
> is the interface of the loadbalancer. Processing limit is from each
> RHCS-node. Disk I/O limit is from the SAN backing the GFS2 in combination
> with the GFS2 (reading should be no issue, heavy writing will trash the
> cluster via locks)

Please think twice of you really need a cluster on the backend web servers. In 
most of the designs you can live without. Which makes live much easier.

Dr. Michael Schwartzkopff
Guardinistr. 63
81375 München

Tel: (0162) 1650044
Fax: (089) 620 304 13

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