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Gazthrak
12-20-2003, 11:47 AM
This is not so much my question than it is a question from my co-worker. I am simply helping him on the research side of this "problem". Here it is...

We are currently using an application with on database. This database is getting large and is also getting to be very important. Hence, we want to have a backup database. Here lies the issue.

You know how Big E-Commerce company X (lets say amazon) has a huge database of customers and such. They probably have backups upon backups. What we are trying to do is have a failsafe where if someone is working off the main database, and in the middle of working on it, it goes down and it moves onto the backup database. My thought on this is to write to both databases at the same time when any work is done. Resource usage is not really an issue.

does anyone have experiance in something like this? How is something like this done on say, amazon.com, and how can an update be done to the primary (or backup) database feasibly when a failure occurs? If I am being too cryptic or if I am not explaining myself correctly, please ask and let me know. I am simply trying to help a friend with a small dilemma in development.

eclectic30
12-20-2003, 03:24 PM
Mirrors. That's your answer for fail over safety. The application server or cgi needs to strike the records accross multiple databases of the same meta data. The cgi or application server must be programmed to ignore failed database servers during the write and to flag it and log the error, and may even be able to send email, or page the Administrator.

Many major SQL based databases have this capability.

This is by no means detailed information so further research is advised.