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Re: Ideas on Failover/Load Balancing
From: |
rader |
Subject: |
Re: Ideas on Failover/Load Balancing |
Date: |
Mon, 24 Oct 2005 04:57:14 -0500 |
> >> I'm planning on deploying a server soon that will be a mirror of my
> >> masterhost. Would anyone be willing to provide some details on
> >> how they've gone about the process of deploying a server for
> >> failover/load balancing?
Keep in mind that there's really no such thing as "masterhosts".
There's "policyhosts" and there's systems listed on the RHS of
server= blocks in copy: actions (which I call "file servers".)
Policyhosts are just file servers that serve up /var/cfengine/inputs
via update.conf.
> > You have a couple of options.
> >
> > 1: Use some sort of network appliance to do the load balancing.
> > This means you'll have to have the same private key on each host
> > or clients will be confused. Also keep in mind that connections
> > coming in from the master server to the clients may come from a
> > different address then the virtual ip. I think the applicance
> > would have to be transparent, otherwise the server will get
> > confused as to the clients ppkey.
> Are ppkeys hardware dependent? That is, if I have a system failover (move)
> to another box (ie. new hardware box, but everything else the same), is it's
> ppkey going to be different?
The ppkey is just a file--and you certainly don't want it to be
different! Restore /var/cfengine (including the policyhost's ppkey)
and cfengine will pick up right where it left off. I did that just
last week (new OS, but the same hardware.)
> I've been thinking about this issue with
> respect to moving virtual machines around to different hardware boxes.
It seems to me that manual failover of the policyhost would be
super easy:
- configure the backup-policyhost to get a complete
mirror of /var/cfengine/masterfiles.
- make the ppkeys on the primary-policyhost and
backup-policyhost the same.
- when the primary-policyhost dies, renumber the
backup-policyhost to the primary-policy
(This is a strategy I've successfully used for master/primary name
server failover for about 18 years now.)
I would think the same idea goes for file servers--except replace
/var/cfengine/masterfiles with the source part of all your copy:
blocks statements.
There's OSS software out there that'll automatically reconfigure a
backup host to take over (e.g. change it's IP address) for a primary
host when a primary host dies, right? Anybody have recommendations?
steve
- - -
systems & network manager
high energy physics
university of wisconsin