The different type of disaster on SQL Server
1. Database Corruption
2. Long Recovery
3. Suspect Database
4. Hardware related Disaster
5. SQL Server does not start / response
This kind of disaster commonly occur due to allocation errors with pages that actually stores the data within SQL Server. It can be avoided by proactive steps like 'Database Maintenance plan in place. Ensuring DBCC Check DB being run against the databases at regular interval.
It being recommended to run the these at lease weekly on medium sized database and fortnightly on huge database. This will definitely highlight the allocation or corruption issues with the databases if there any before the cause harm. Hence corrective action could be taken at ample time ahead.
More on http://support.microsoft.com/default.aspx?scid=kb;en-us;307775