Storage Area Networking

The advantages of a SAN implementation address most of the challenges faced with distributed storage models.

Support for Multiple Architectures and Operating Systems - High-end storage subsystems are able to support various server architectures and operating systems with a single storage subsystem.
Fibre Channel Interface - The Fibre Channel interface is the interface of choice in a SAN. It overcomes many of the device limitations hampering other interfaces.
High Data Availability - With high availability, data is available to LAN users even in the event of hardware or network failures. To achieve high availability, SAN optimized storage devices implement hardware based RAID and can be used as the shared storage for failover clusters. In addition, a SAN can be designed to offer redundant paths between attached devices. Even in the event of component failure, a SAN's storage resources can remain available to users.
Centralized High Speed Backup - A SAN allows for numerous servers to be attached to a single tape library through a high-speed connection. Previous solutions compromised either centralization (direct attach or local backup) or performance (network backup). SAN offers the best of both worlds.
Easier to Manage - Because the storage is consolidated into an independent subsystem, it is easier to centralize, maintain and manage than storage attached to numerous distributed servers.

	DAS	NAS	SAN

Primary Function	SCSI or Fibre Channel disk enclosures attaching directly to a server to provide storage expansion. Access to files is through the LAN/WAN.	Specialized appliance providing consolidated networked file services for clients and servers. Storage is accessed directly across a LAN/WAN.	Consolidated Fibre Channel storage for servers. Storage is accessed across a dedicated storage network.



Installation	Can be installed easily but the entire server must be brought down to install.	Can be installed quickly and easily without downtime.	Installation can be complex.



Scalability	Limited number of disk enclosures can connect to a server.	Multiple NAS appliances can be added to the network.	Storage can be scaled by adding additional Fibre Channel switches and storage devices.



Backup Resources	Backup devices can directly attach to the server or through LAN/WAN.	Backup devices can directly attach to mid-range NAS or through LAN/WAN.	Backup devices can directly attach to server or through Fibre Channel fabric. A LANless backup scheme is employed.