Relational database or NoSQL database

I'm about to implement a system which will need to receive a lot of calls per day and save them. It needs to bring information to internet users as well (something like a call center or a 911). I've two doubts: 1) I'm between using SQL Server, MongoDB or Cassandra, 2) If it's SQL Server I'm between using and ORM like NHibernate or Entity Framework.

Any suggestions will be appreciated. Thanks in a开发者_运维问答dvance. Daniel

1. Can't tell without more detailed requirements (e.g., volume, etc.) I'll bet any of them will "work". You should pick the one you know best, implement it, and get some data.
2. You don't need an ORM layer if you don't have objects, especially those with complex relationships.

Why dont you do both? For every write or update you make in cassandra, fire a jms message. The consumer of that jms message can read from cassandra and update your RDMS (mysql, oracle, etc).