A NAS is a single storage device that operate on data files, while a SAN is a local network of multiple devices that operate on disk blocks. A SAN commonly utilizes Fiber Channel interconnects. A NAS typically makes Ethernet and TCP/IP connections.
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NAS |
SAN |
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| 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 data, etc.), and handles security, user authentication, file locking | A SAN addresses data by disk block number and transfers raw disk blocks. | |
| 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) are done on files, not blocks, for a 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. | |
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