What is the difference between SAN & NAS?

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 Fibre Channel interconnects and iSCSI. A NAS typically makes Ethernet and TCP/IP connections with mostly NFS Protocol.

With Storage Area Networks (SAN), we typically see this solution used with medium-to-large size businesses, primarily due to the larger initial investment.  SANs require an infrastructure consisting of SAN switches, disk controllers, HBAs (host bus adapters) and fibre cables.  SANs leverage external RAID controllers and disk enclosures to provide high-speed storage for numerous potential servers.

The main benefit to a SAN-based storage solution is the ability to share the storage arrays to multiple servers.  This allows you to configure the storage capacity as needed, usually by a dedicated SAN administrator.  Higher levels of performance throughput are typical in a SAN environment, and data is highly available through redundant disk controllers and drives.  The disadvantages include a much higher startup cost for SANs, and they are inherently much more complex to manage.  The following diagram illustrates a typical SAN environment.

A third type of storage solution exists that is a hybrid option called Network Attached Storage (NAS).  This solution uses a dedicated server or “appliance” to serve the storage array.  The storage can be commonly shared to multiple clients at the same time across the existing Ethernet network.  The main difference between NAS and DAS and SAN is that NAS servers utilize file level transfers, while DAS and SAN solutions use block level transfers which are more efficient.

NAS storage typically has a lower startup cost because the existing network can be used.  This can be very attractive to small-to-medium size businesses.  Different protocols can be used for file sharing such as NFS for UNIX clients and CIF for Windows clients.  Most NAS models implement the storage arrays as iSCSI targets that can be shared across the networks.  Dedicated iSCSI networks can also be configured to maximize the network throughput.  The following diagram shows how a NAS configuration might look.

SAN & NAS both are two different ways of accessing data. SAN is meant for Block access whereas NAS is used for File access.

In todays world most of the storage vendors are providing both SAN (FC & iSCSI) & NAS (CIFS & NFS) protocols in a single storage called a Unified Storage. This unification was initiated by NetApp after which every other vendor followed.

• NAS is Network Attached Storage and SAN Storage Area Network
• A NAS, known as  “filer”, is a file storage device and SAN is  block storage device.
• Protocol for SAN : iSCSI, Fibre Channel, SAS, eSATA, USB  and for NAS: NFS, SMB / CIFS a AFP and FTP.

NAS is storage connected to lan switch and accessed by TCP/IP.

SAN is storage connected to special switch or san switch, it can be conected either fibre or iSCSI (SCSI over TCP/IP)

NAS and SAN can be mainly differentiated in the way they are attached to the server. NAS is usually the disk(s) on another machine,  that is mounted as shared drive or like an nfs volume. 

SAN disks usually appear to the system as a directly attached storage, that is to the server the SAN storage device will appear like its local hard disk. 

in simple words, SAN for more size files and have many IN/OUT Transactions.NAS mainly for simple archiving/Backup purposes.