According to Executive Chairman of Google Eric Schmidt, every two days we create as much information as we did from the dawn of civilization up until 2003. It is approximately 5 Exabytes (1 Exabyte = 1024 Petabytes, 1 Petabyte = 1024 Terabytes). Every human being, who has any digital device, is essentially a content creator. Data center managers are facing this arduous task of providing low-cost, high-performance information management solution.
Storage area network (SAN) carries data between servers and storage devices through fibre channel switches. It enables storage consolidation and allows storage to be shared across multiple servers, which are spread geographically. Network attached storage (NAS) is an IP-based single storage device attached to a local area network. Let us compare these two technologies side-by-side:
SAN | NAS |
| Server class devices that are equipped with SCSI Fibre Channel adapters connect to a SAN. | Almost any machine that connects to a LAN. |
| Protocols: Fibre Channel Protocol (FCP), which is implementation of serial SCSI-3 over FC. | NAS solutions use TCP/IP and NFS/CIFS/HTTP based networks |
| A SAN addresses the data by logical block numbers, and transfers the data in (raw) disk blocks. | A NAS identifies the data by file name and byte offset, transfers file data or metadata, and handles security, user authentication, file locking. |
| File Sharing is operating system dependent, and may not exist for all operating systems that are being used. | A NAS allows greater sharing of information, especially among different operating systems. |
The SAN servers manage the file system. | File system is managed by the NAS head unit. |
| Backups and mirrors require a block by block copy operation. A mirrored system has to be either identical, or greater in capacity (compared to the source). | Backups and mirrors are generated on files, not blocks (this may save bandwidth and time). |
| SAN uses single-mode or multi-mode fiber cabling depending on the environment. | NAS uses existing IP networks like Gigabit Ethernet, Fast Ethernet, ATM, and Fiber Distributed Data Interface (FDDI). |
| Connectivity options: point-to-point, FC-AL (Fibre Channel Arbitrated loop), FC-SW (Fibre Channel Switched Fabric). | Gateway NAS, Integrated NAS. |
| Benefits: Availability, reliability, scalability, performance, manageability, return on information management. | Supports comprehensive access to information, improved efficiency, improved flexibility, centralized storage, simplified management, scalability, high availability, security. |
For more information:
- How much data is that: http://www.jamesshuggins.com/h/tek1/how_big.htm
- SAN and NAS Solutions - Introduction, Topology, and Terminology: http://www.fortuitous.com/docs/primers/SAN_NAS_Intro.pdf
- Information Storage and Management: Storage, Managing, and Protecting Digital Information. EMC Education Services, Wiley, ISBN: 978-0-470-29421-5
Technical Committee responsible for fibre channel interfaces: http://www.t11.org/index.html
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