>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?

A Web app is disconnected most of the time. Rather than # of users, you could estimate number of web server hits (e.g. page views) per user per minute or hour, times average hit size, times 2,000, then convert that to hits/sec and bandwidth/sec.

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

USB hard drive is increasingly popular, tape still common. You might want to look at scheduled armoured car service to another of your facilities (if there's more than one) or to a secured storage facility.

If the data are not too large you could set up a secured server for backup at another of your facilities and use either a private data connection or an encrypted channel through the public Internet to copy data across.

Some commercial services offer "online backup" but I doubt that your organization would consider them secure enough for "incredibly sensitive" data.

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

Is this an app that's already pre-written, and you're buying and installing it? If so, ask the vendor. Otherwise, without a lot more information all anyone can say is "it depends".

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

1M rows is actually a pretty small database these days. As a ballpark figure, if each row was a kilobyte (1K), the database would be roughly 1GB. If the app is pre-written, ask the vendor.

Can you give us any back story? If you're going to have 2,000 simultaneous web users, an app like that can easily cost hundreds of thousands of dollars, plus hardware, installation & configuration, ongoing support, consulting etc. If you've already got an app in mind, for that kind of money the vendor should be able to answer the types of general questions you're asking. If you don't already have the app and need to get it developed, you can ask questions like these in your RFP.