>Our organization is currently facing the possibility of hosting a large-scale .NET web application with a SQL back-end. The application must be able to accommodate 2,000+ simultaneous users and the database itself will have around 1,000,000 records.
>
>We have a number of questions, and would greatly appreciate any suggestions you may have, regarding:
>1.) How much bandwidth will this require?
>2.) What about backup solutions (on-site and off-site)? This data is incredibly sensitive.
>3.) What kind of web servers and load balancing scenario would we need?
>4.) How much space would we roughly need for data storage?
>
>Thank you for your time.
>
>Matthew

We have recently completed a similar project. We had a VFP app that ran at 750 client sites with +- 2000 users. Our data model was a little smaller (about 150 tables). Paul has given you some excellent advice. I'll add some based on our experience.

As Paul noted, many features of a desktop app do not translate well to a web-based app. AJAX type techniques help in some of these scenarios, but you may have to rethink some of the features of your UI.

Since we are a pretty small shop ( 3 developers ) we outsourced (off shore) development of the web app. This "worked" in the sense we had a "working" web application in a much shorter time than we could have developed it on our own. The down side is the maintenance nightmare we have experienced. I won't go into all the details here except to say that I have learned a lot about how not to do things in DotNet. In all fairness, I have also learned a lot from their code. Unfortunately, the skilled developers were far outnumbered by the rookies.

We migrated our clients onto the new system over 12 months. Our migration process included importing some of the data from the VFP app into the new app. Our migration process was deliberately slow. Our initial converts knew they were beta testers in actuality. It allowed us to identify and deal with performance bottlenecks w/o 100s of users complaining.

> 1.) How much bandwidth will this require?

We currently have 10 mbps and have no bandwidth issues. We serve on average 80,000 pages/day, about 60KB/page. Even though we have 2000 potential concurrent users we TYPICALLY have about 70 concurrent users logged in. Usage of our app is not evenly distributed. We have enough bandwith to ensure good performance during peak usage so we are paying for bandwidth we don't necessarily need during off hours.


> 2.) What about backup solutions (on-site and off-site)? This data is incredibly sensitive.

I'm a developer, not a DBA, so I don't know all the details. We do backups to NAS devices both locally and off-site over a VPN.


>3.) What kind of web servers and load balancing scenario would we need?

We worried quite a bit about this, but it hasn't been an issue. We've never stressed the web server. Our web server is a VM that is allocated 4 single core CPUs and 4 GB RAM.


>4.) How much space would we roughly need for data storage?

You will need to estimate :-). We maintain 2 databases, "Active" and "Archive". Active currently consumes about 4 GB. Archive consumes about 9 GB. Storage is on a SAN which allows us to add drawers as needed. If you go the SAN route, ensure your vendor configures the SAN for SQL storage, not as a file server. Our SQL server is 4 X quad core with 16 GB RAM. You can't have too much RAM!


Many of our design decisions were based trying to make a web app perform like a desktop app. Our clients pay to use this system and performance is critical. Our goal is to serve up a page in less than 1 sec.

Please ask more questions. It was a challenging project for us, but in the end, our clients are pleased.