NAS are typically used for simple ways of storing fast data for multiple clients at the file level thru the network. DAS are directly attached to a server with a group of hard drives and is normally access through the attached servers. SAN, is a dedicated high availability for block level data transfer. SAN are the ideal way to ensure predictable performance and reliability.
Managing data does not have to be hard. With a DAS you can easily allocate storage provisioning and scale on the fly when on the need.
Data is vital to all organization. SAN can provide the security and performance with the RAID arrays built in and fiber channel speed.