I am in the process of designing a high availability system using Apache , Tomcat and MySQL. Of course the OS is Linux

There will be one Apache server serviced by two Tomcat servers. MySQl will be installed on each Tomcat server with replication enabled. This is a production system to which almost 1000 users will be connecting simultaneously.

This would mean the http request will be with processed by
[Browser] ---> [Apache] -----------> [Tomcat1+MySQL1]
or
[Browser] ---> [Apache] -----------> [Tomcat2+MySQL2]

I am not sure what kind of server configuration I should have for these servers. Should the server have single CPU or multiple CPUs ? How much of an advantage does having multiple CPU server offer to the web server as compared to one with a single CPU.
How much RAM and Hard Disk should they have. Does anyone know how much memory is consumed by Apache-Tomcat in order to maintain a http session.

I have been able to find some documentation regarding this but it comprehensive enough. There is quite a bit of generalization and most give a general purpose server setup.
Also for the memory requirements people suggest using 'ps' to find the utilization by a httpd/tomcat process and proportionally calculate the total memory requirement.

Thanks

I can't tell you specifics about Apache Tomcat as I've had no expeience with it. Although as far as the hardware goes...

If you want to support a lot of simultaneous sessions then it'll be worth you investiging in a multiple processor machine as they behave much better under load simply because you can execute processes in parallel. It's worth getting as much RAM as you can, the exact amount needed will be dependent on what you're going to be running on Tomcat. Your code will probably use more memory than anything else so this is something you'll need to work out by running your code and seeing what resources it uses.

The same argument will apply to disk space, although if you are looking at a large server you'll want to invest in a decent set on disks on a nice RAID so you don't end up with your disk IO being your bottle neck.

Are the two servers going to be mirroring one another with load balancing or are they going to be seperate? What speed will your connection to the web be? There is no point in specing up a monster server then putting it on the end of 1MB connection!

HTH

Jamie...

Apache will be the one doing the load balancing and the failover.
But I have got a good idea of what is required. Thanks a lot.