Vendors

I am designing a Storage area . I am student working on this i dont know much about various vendor based servers. so how should i have to decide which vendor to go ? as there are many vendors offering servers ? my applications are cad and database. both uses same storage but different servers, application and data servers are different. i am almost designed model . but now choosing vendors for servers and chossing which SAN to implement like iSCSI san or FC or Ip storage. any help appreciated.