[chmac]

Running mysqldump on a database the size of CouchSurfing's is a real problem. It's a resource hog. To properly back up a consistent data image you need to use locking, which prevents writes to your database while the backup is running. That causes downtime on every backup, not ideal.

Likewise, when backing up 100s of GiBs of data, a simple tar gz is not suitable. More sophisticated strategies need to be used when the data becomes that big.

I've found http://HighScalability.com to be a great source of information on building scalable applications.