What's the "master" database in SQL Azure for? I just created a subscription and once I created a "new SQL Server" I immediately got "master" database with 1GB size. That database can't be deleted - "delete" button is not active in the management portal.
When I tried to deploy a .dbproj project there Visual Studio said it "couldn't deploy to a system database".
Can I use that database for storing my data? Do I create a new database instead?
master is a required system database that's responsible for holding info about all the the other database on the server instance, system metrics/config, managing logins & database creation etc, its read-only and can't be removed.
You will need to create a new database and deploy to that.
Just a note: you will not be charged for the master DB.
The master database records all the system-level information for a SQL Server system. This includes instance-wide metadata such as logon accounts, endpoints, linked servers, and system configuration settings
来源：https://stackoverflow.com/questions/6650357/please-explain-sql-azure-master-database