Move / Migrate DB's Without Disturbing Existing

Typically small companies or small projects which use SQL Server / IIS / File Shares / .NET solutions deploy these apps on a single server many times using just one IP address and the NETBIOS name of the server for both IIS / SQL. Many times there is no use of DNS and even when there is everything is mapped to the server/netbios name.

As environments grow and there is a requirement to create an n-tier server setup possible due to new security requirements, extention of the intranet to the internet, or to scale out an application you may need to split IIS / SQL into different servers. The question then becomes how do you do this without affecting existing services and you want to have minimal down time without having to change all connection information within deployed apps until you have time to review the changes carefully.

First let me begin with how to move IIS away from SQL and then I'll discuss the reverse.

The best way I've found to control the move of IIS sites is by assigning each site it's own ip address / dns host record and adding the ip address to the server network card and IIS site. Now each time you need to move 1 or more sites you can simply replicate the site to another server and change the dns ip pointer to the new pointer. If you have existing sites which were not setup in this fashion you can also move them to a new server, create a site with name of the old netbios machine name, and redirect the default web site to this new site.

Now you successfully isolated SQL Server from IIS/.NET apps you can take your time and correct the apps to use the new dns entry in connection strings instead of using the netbios name of the machine. Once you have corrected the app you can turn off any redirection.

Now let's assume you have the opposite scenario where you started off with a small server and your SQL database server now requires a server with more memory / more processors and you want to keep IIS / FileShares were they are and want to move SQL Databases to a new server. As I mentioned above a good way to do this is by setting up each database with it's own dns entry a very effective redirection mechanism. However you are may be inheriting a system which does not employ this mechanism and again uses the default netbios machine name, furthermore this may get more complicated because there may be multiple instances of SQL Server running on different port numbers.
You could use SQL Aliases on the clients to redirect connections to the newly created instances but this would require changing every pc and IIS server and it would be cumbursome to manage. It would have been nice if microsoft provided a way to redirect from the server just like IIS does but they did not. A product which will help you setup a server based redirection of ports 1433/1434 and/or any other ports is called porttunnel by steelbytes.com. Once you've installed the redirecting service on the server all new requests on port the ports selected will be redirected to the new server which I recommend be redirected to their own dns entries and this will buy the applications developer time to change their applications.

I would like to hear any comments or experiences with this that any of you may have had or if anyone has found a better solution. I'm in no way associated with the product / or company mentioned above just found it to be a good solution.

Best Regards,
Valter Borges