NAS – Network Attached Storage:

1. Any machine that can connect to the LAN can use NFS, CIFS or HTTP protocol to connect to a NAS and share files.
2. A NAS identifies data by file name.
3. NAS allows greated sharing of information between disperate Operating systems such as Unix and NT.
4. File System handled by NAS head unit.
5. Backups and mirrors are done on files and not on blocks for savings in bandwidth and time.

SAN – Storage Area Network:

1. Only server class devices with SCSI Fibre channel can connect to the SAN.
2. SAN address data by disk block number and transfer raw disk blocks.
3. File sharing is operating system dependent and does not exist in many Operating systems.
4. File system handled by servers.
5. Backups and mirrors requires a block by block copy even if the block is empty.

Types of networks supported
NAS uses TCP/IP Networks: Ethernet, FDDI, ATM (perhaps TCP/IP over Fiber Channel someday)
SAN uses Fiber Channel

The Protocols
NAS uses TCP/IP and NFS/CIFS/HTTP
SAN uses Encapsulated SCSI

NAS works best for these types of applications:
File serving
File sharing
Users’ home directories
Content archiving
Metadata directories
E-mail repositories, such as enterprise .PST files
GRID computing (using 10 Gigabit Ethernet)
Peer-to-peer data sharing

SAN works best for these types of applications:
Databases
Server clustering
Messaging applications
Backup
Data replication
GRID computing
Data warehousing
Recovery archives