NAS vs. SAN Network Storage

There has been some debate for years about which type of network storage is the best way to go. It will depend on your environment just like most computing decisions. Here are the main differences between NAS and SAN network storage solutions.

NAS Network-Attached Storage

* NAS is a defined product that sits between your application server and your file system.
* A box that acts like a hard disk to the network, while in reality is a computer with hard disks and a network port that is pre-configured to act like a file server.
* To the user, the file on the remote computer could be used just as if it were on the local hard disk.
* 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.
* NAS is cheaper, but a slower solution that also requires bandwidth on the network for the extra I/O.

SAN Storage Area Network

* SAN is a defined architecture that sits between your file system and your underlying physical storage.
* Usually installed because existing or standard networks cannot handle the requirements of certain applications, e.g. for bandwidth
* This allowed the sharing of disk space among multiple computers, which lead to better performance and enabled more fault tolerant computing through the use of server clusters.
* 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
* SAN is more expensive, much faster, but requires a lot more maintenance. Each host system will have a special card that would be hooked up directly to a SAN or some sort of SAN Switch.

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

* 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
* Any application that requires low latency and high bandwidth for data movement.