On 3/4/2011 1:18 PM, James Nguyen wrote:
>
> You want two boxes that run both haproxy + keepalived. This way you
> get the load balancing (HAProxy) plus the high availability
> (Keepalived) using a shared virtual IP for your two boxes. You can do
> maintenance on either one while traffic still remains active.
>
> I don't have metrics to spec out the boxes, but given your traffic
> load you mentioned you don't need hefty boxes at all. Just get
> yourself a box with some Gigabit interfaces which I'm sure they all
> are these days. A single socket with 4 cores is more than enough.
> You can probably even do with 2 cores. Someone can correct me on that
> if they think the solution requires a lot of CPU. Memory wise I think
> machines come with at least 4Gb these days. That should do. You can
> probably both boxes for around 2k?
>
> You already know how much F5 or any of those guys cost per device. =)
>
F5's are one of those things where if you have to ask the price you
probably can't afford it... But they do provide a very nice web
interface to control the pool members and virtual interfaces, something
I haven't seen on free alternatives, and if you are big enough to have
multiple locations they can propagate their server state info to their
global DNS servers (also expensive) to control balancing/failover across
sites.
For a couple of boxes that can work independently, I'd just use round
robin DNS and also use heartbeat to float the IP's to the backup on
outages. That way you normally share the load for performance but if
one fails or is shut down gracefully, the other one will still handle
things for both IP targets. If your application maintains any session
state you'll need to work out a way to keep it in sync or after the
initial connection, redirect to a specific machine and live with what
happens when it goes down (which might not be that bad, maybe just a new
login when they try to come back).
--
Les Mikesell
lesmikesell at gmail.com