couple questions...

[Ricardo Kleemann]

Hello Graeme,

Thank you for your comments.

More comments below...

>> Just wondering if that would work...
>
> Short answer: yes :)
>
> You will need to solve a few minor problems, as you'll end up with a
> system with a pair of VIP addresses for your clients to connect to.
> That means you'll need to do something like DNS round-robin; in turn
> that means you'll need to endure the outage if  (for example) one of
> your servers has to be taken (or goes) offline and stops responding.

So you mean that round-robin DNS won't really work? I've always wondered how 
resolution of round-robin DNS works... do lookups always swap between the 
different IPs with each subsequent lookup?

So for example, if I have round-robin DNS jumping between servers A/B, and A 
goes down... if a client resolves the hostname to A, it will fail to 
connect, then if it retries, will the hostname next time resolve to B?

>
> Alternatively you'll need something to manage both the LVS and HA
> aspects of the system, like keepalived or heartbeat.

Are these really necessary? If all I'm using it for is for the load 
balancing, and LVS is capable of detecting a server going down, it will 
simply direct connections to the alternate server. What would I use 
keepalived or heartbeat for?

>
> You will also need to solve the potential problem of both servers being
> configured to handle both VIPs as both LVS director and realserver -
> this one can tie you in knots very easily. I usually manage it with
> fwmarks on the input interface (the one facing the clients).

If I understand correctly, the realservers are the DB servers. The LVS 
director is on the app server, which directs connections to one of the 2 DB 
servers. Why would there have to be any sharing of VIPs? I don't think 
either of the servers would be both director and realserver, would they?

Thanks again!
Ricardo