The Key Differences Between SAN, DAS, and NAS

• Direct-Attached Storage(DAS)

The most common form of server storage today is still direct attached storage.
The disks may be internal to the server or they may be in an array that is connected directly to the server
Either way, the storage can be accessed only through that server.
An application server will have its own storage; the next application server will have its own storage;
and the file and print servers will each have their own storage

• Storage Area Networks(SAN)

A SAN allows more than one application server to share storage.
Data is stored at a block level and can therefore be accessed by an application, not directly by clients
The physical elements of the SAN (servers, switches, storage arrays, etc.) are typically connected with Fibre-Channel – an interconnect technology that permits high-performance resource sharing
Storage can be added without disrupting the applications, and different types of storage can be added to the pool.


A storage area network (SAN) is a dedicated network that provides access to consolidated, block level data storage. SANs are primarily used to make storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear like locally attached devices to the operating system. A SAN typically has its own network of storage devices that are generally not accessible through the local area network by other devices
In storage networking terminology, a Storage Area Network (SAN) is a high-speed subnetwork of shared storage devices. A storage device is a machine that contains nothing but a disk or disks for storing data.

A SAN's architecture works in a way that makes all storage devices available to all servers on a LAN or WAN. As more storage devices are added to a SAN, they too will be accessible from any server in the larger network. In this case, the server merely acts as a pathway between the end user and the stored data.

Because stored data does not reside directly on any of a network's servers, server power is utilized for business applications, and network capacity is released to the end user.

• Network Attached Storage(NAS)

A NAS appliance is a simplified form of file server; it is optimized for file sharing in an organization.
Authorized clients can see folders and files on the NAS device just as they can on their local hard drive
NAS devices are frequently used to consolidate file services.
To prevent the proliferation of file servers, a single NAS appliance can replace many regular file servers, simplifying management and reducing cost and workload for  the systems administrator.
NAS appliances are also multiprotocol, which means that they can share files among clients using Windows® and UNIX®-based operating systems.

Reference:
http://smbtechconnect.securelement.com/2008/03/key-differences-between-san-das-and-nas.html

• An optical jukebox is a robotic data storage device that can automatically load and unload optical discs, such as Compact Disc, DVD, Ultra Density Optical or Blu-ray disc and can provide terabytes (TB) and petabytes (PB) of tertiary storage.

https://en.wikipedia.org/wiki/Optical_jukebox