high performance, highly available web clusters

[David Wilk <myca@cia-g.com>]

Howdy all,

I am thinking about how to increase the capacity of a web cluster and
was wondering if anyone out there had any experience with this type of
thing.

The cluster is comprised of a load-balancer, several web servers
connected to a redundant pair of NFS servers and a redundant pair of
MySQL servers.  The current bottle-neck is, of course, the NFS servers.
However, the entire thing needs an increase in capacity by several
times.

First of all, the web servers need a hardware upgrade and increase in
total number.

The expensive option would be to add a high-performance SAN which would
do the trick for all of the servers that required high-performance
shared storage.  this would solve the NFS performance problems.

However, for alot less money, one could simply do away with the file
server entirely.   Since this is static content, one could keep these
files locally on the webservers and push the content out from a central
server via rsync.  I figure a pair of redundant internal web server
'staging servers' could be used for content update.  Once tested, the
update could be pushed to the production servers with a script using
rsync and ssh.  Each server, would of course, require fast and redundant
disk subsystems.

I think the lowest cost option is to increase the number of image
servers, beef up the NFS servers and MySQL servers and add to the number
of web servers in the cluster.  This doesn't really solve the design
problem, though.

What have you guys done with web clusters?

thanks!
Dave
-- 
*******************************
David Wilk
System Administrator
Community Internet Access, Inc.
myca@cia-g.com