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Hi Simon,
>
>
> Hi Gerd,
>
> On Wed, Sep 02, 2009 at 11:52:17PM +0200, it-intuition wrote:
> > Hello,
> >
> > we are currently using lvs for balancing two webservers by
> using the
> > wrr scheduler in combination with persistance. Now we want
> to modify
> > our setup to use one primary webserver and a secondary
> webserver as a
> > backup server. My idea was to set the weight of the primary
> webserver
> > to 1000 and for the backup server to 0.
> >
> > These are the question that came up in my mind:
> >
> > 1. How will this setup behave if the primary webserver is down?
>
> I suspect all connections will fail.
That's what I suspected too.
> > 2. How will this setup behave if the primary webserver is up again?
>
> As it did before the primary went down.
> >
> > 3. Does a weight of 0 mean, that no connection to the backup server
> > can be made (if the primary webserver is down)?
>
> A real-server with a weight of 0 won't get any new
> connections, unless they are associated with a recent
> connection and the service is marked as persistent.
>
> In your case, this should mean no, no connections will be
> sent to the backup server.
>
> In short I think the basic effect of this setup would be the
> same as not having the backup server in the pool at all.
>
> > The last question may sound stupid, but I read that a
> weight of 0 is
> > often used to silently take a server out of a pool. So I think a
> > weight of 0 prevents clients to connect; which is not the effect I
> > want for our setup.
> >
> > Any help or comments would be appreciated.
>
> I think that a better strategy is to have a higher level
> monitor looking at your servers and inserting the backup
> server into lvs as needed. ldirectord and keepalived should
> both be able to do this.
Ah, looking from the other side onto the problem. That'a good idea.
I think this is the way we go further.
> Alternatively, explicit support for this kind of backup
> server arrangement could be added to lvs. But it would rely
> on a fairly low-level view of weather the primary is up or down.
I wouldn't go that far.
Ok, if it would be implemented, fine. :)
Thanks!
Gerd
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