Varnish and Load Balancing

[Juergen Schreck]

Hello -

I'm currently researching my options to implement varnish into our hosting recipe.

We provide load-balanced hosting services for Magento. We run a software load-balancer that handles all of our dedicated and VPS nodes. We've optimized each Magento instance such that we're using Apache/mod_php for the dynamic requests and nginx on a separate port and cookieless domain for all static assets. So we're not employing an reverse proxy methods at this point. Apache does all the php stuff and we're using memcached to help it out on the backend.

I could a Varnish server picking up a lot of slack of what we do there and improve upon it. I don't know that I'd want it to cache assets, because that'll be moving to a CDN. But with the Page Cache Powered By Varnish Magento module, I think it could work very nicely.

What I'm pondering is whether I should still run load-balancers in front of a Varnish server or let the Varnish built-in balancer do that work.

I'm also not sure how much a single Varnish server could provide with multiple dual-node vps backends and how I would scale it as the number of sites/vps grows.

Any suggestions to that layout? Right now it seems to me like I'd have some redundant puzzle pieces… Would appreciate your thoughts to help me sort it out.

Thanks,
Juergen