What is the difference between SAN and NAS ?

Introduction

At first glance, NAS and SAN might seem almost identical, and in fact, many times either will work in a given situation. After all, both NAS and SAN generally use RAID connected to a network, which they are backed up onto tape.

Almost any machine that can connect to the LAN (or is interconnected to the LAN through a WAN) can use NFS, CIFS or HTTP protocol to connect to a NAS and share files. Only server class devices with SCSI Fibre Channel can connect to the SAN. The Fibre Channel of the SAN has a limit of around 10km at best A NAS identifies data by file name and byte offsets, transfers file data or file meta-data (file’s owner, permissions, creation date, etc.), and handles security, user authentication, file locking A SAN addresses data by disk block number and transfers raw disk blocks.

Comparison

The administrator of a home or small business network can connect one NAS device to their LAN. The NAS maintains its own IP address comparable to the computer and other TCP/IP devices. Using a software program that normally is provided together with the NAS hardware, a network administrator can set up automatic or manual backups and file copies between the NAS and all other connected devices. The NAS holds many gigabytes of data, up to a few terabytes. Administrators add more storage capacity to their network by installing additional NAS devices, although each NAS operates independently.

NAS

A NAS allows greater sharing of information especially between disparate operating systems such as Unix and NT. File Sharing is operating system dependent and does not exist in many operating systems. File System managed by NAS head unit File System managed by servers Backups and mirrors (utilizing features like NetApp’s Snapshots) is done on files, not blocks, for savings in bandwidth and time. A Snapshot can be tiny compared to its source volume. Backups and mirrors require a block by block copy, even if blocks are empty. A mirror machine must be equal to or greater in capacity compared to the source volume.

SAN

Whereas in SAN, Only server class devices with SCSI Fibre Channel can connect to the SAN. The Fibre Channel of the SAN has a limit of around 10km at best. A SAN addresses data by disk block number and transfers raw disk blocks. File Sharing is operating system dependent and does not exist in many operating systems. File System managed by servers. Backups and mirrors require a block by block copy, even if blocks are empty. A mirror machine must be equal to or greater in capacity compared to the source volume.