Difference between San VS NAS ?

Q. What is Difference between SAN and NAS?

A. NAS is a single storage device which operates on data files. SAN is a local network of multiple devices which operate on disk blocks

Points for SAN :

1. It uses Fibre Channel
2. Encapsulated SCSI
3. Just the server class devices with SCSI Fibre Channels can connect to the SAN. The Fibre Channel of SAN has a limitation of approx 10KM.
4. A SAN addresses data by disk block number and transfers raw disk blocks 
5. File sharing depends on the OS and does not exists in many operating systems
6. File systems managed by Servers 
7. Backup and mirror requires a block by block copy, even if blocks are empty. A mirror machine must be of equal to or greater in capacity compared to the source volume.

Points for NAS :

1. It uses TCP/IP Networks – Ethernet, FDDI and ATM
2. Protocols used – TCP/IP and NFS/CIFS/HTTP
3. Almost any machine which can get connected to LAN (or is interconnected to the LAN through WAN) can use NFS, CIFS or HTTP protocol to connect to a NAS and share Files. 
4. A NAS identifies data by file name and bytes offsets, transfers file data or file meta-data (File’s owner, permissions, creation data, etc.) and handles security, user authentication, file locking.
5. A NAS permits better sharing of information especially between disparate operating systems such as UNIX and NT
6. File systems managed by NAS head unit.
7. Backups and Mirrors (utilizing features like Netapp snapshots) are done on files, not blocks, for a savings in bandwidth and time. A snapshot can be tiny compared to source volume.