Load balancing geographically distributed nodes with varnish - a good idea?

[Thomas Prommer]

Varnish Community,

We are managing a cluster farm of 6 nodes that are geographically
distributed across Europe (Amsterdam, London, Lisbon, Frankfurt, Zurich,
Milan) delivering our internationalized application for the appropriate
CCTLD for such nodes. All nodes have the same server image and application
deployed. The server distribution is critical to ensure low latency in local
markets as well as for SEO reasons.

The application is a simple LAMP application (no centralized data) that is
using Varnish and Lighttpd Fast CGI for optimal scaling. However, we still
run into scaling issues were essentially one node gets hit hard with local
traffic while all the other severs are pretty idle.

Our question is if there is a common recommendation of load balancing a
server cluster where the servers are geographically distributed and also if
varnish or the lighttpd fastcgi server would be more appropriate to carry
out the load balancing?

We know that both systems allow for load balancing but we are concerned that
simply load balancing the IPs of geographically servers wouldn't perform too
well because an additional round trip to a remote server location would be
introduced.

In a nutshell, our questions are:

Are there any good strategies around load balancing geographical distributed
servers?
What are the evaluation points for deciding if either Varnish or Lighttpd
FastCGI would be more appropriate to own the load balancing responsibility?

Thanks /Thomas
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://www.varnish-cache.org/lists/pipermail/varnish-dev/attachments/20110915/4f44052b/attachment-0003.html>