My Question is:

I consider tfs app server failover scenario:

I have backuped attached tfs collections (databases). I cant afford to detach for each backup. If app server will crash I should recover the backups (attached collections) to new app server. I want to test this failover scenario. 

Please help me how can I achieve this. I don't want to deatch the database from project collection. If something goes wrong with app server, I should be able to take the attached backup directly from SQL rather than the backup of deatched collection which any way it will work.

Thanks.