difference between SAN and NAS

[Baiju Kumar.B_1]

Dear all,
i am new in storage
plesae give the detailed information between SAN and NAS,what type of operating system is using in nas .what is the diffence between normal windows server os and nas operating system
regards
Baiju Kumar.B

[Jefferson Humber]

A SAN means that node are connected to the storage using Fibre Channel (FC) usually via an FC Switch.

NAS on the other hand would use Ethernet and wonderful things like CIFS/NFS e.t.c to share the data out.

NAS is generally cheaper than SAN, but you get what you pay for in my opinion.

NAS O/S's are usually cut down http managed versions of the real McCoy designed specifically for the NAS job. Microsoft have there own flavour, see their site for details.

There are plenty of resources on the web for the pro's & Con's of both a quick Google search will come up trumps for you.

[Steven Clementi]

SAN = Storage Area Network
NAS = Network Attached Storage


The main difference between a SAN and a NAS is that 1. they are 2 totally different things. A SAN is an infrastructure of client servers and target storage devices that interact with each other. A NAS is usually a single device that is set up to serve out Storage. A NAS is sometimes connected to a SAN environment.

Typically, a NAS runs a special version of a particular OS. In the case of Windows, the current NAS os is Windows 2003 Storage Server. NAS's come in different flavors though. NAS's usually connect up to MASS storage devices like a MSA500 or MSA1000/1500 or an EVA or a XP or some other SAN based Storage device. They then serve out their available storage via the network in the form or http or ftp or ntfs or nfs and sometimes other types of storage protocols.

The main difference between a normal server and a NAS "head" is that the NAS is finely tuned for "File Sharing" where a regular server can do anything. File Sharing, Printer Sharing, Applications, Databases, etc.


Steven

[Bill Costigan]

Another way to look at it is a SAN presents a disk to the server just like a physical disk mounted in the system. The server communicates a disk level using SCSI commands (e.g, read X bytes starting at disk sector Y, Write X bytes strating at disk sector Y.) The SCSI commands are packaged in fiber channel packets and sent to the array. The file system talks to SAN disk with scsi drives just like real disks.

The NAS uses filesystem access. The commands are things like read a directory, open a file, read a record, etc. In fact the NAS is accessed via everyday remote file access using protocols such a NFS or CIFS. NAS devices look like shared filesystems and SAN devices look like disks.

A NAS device can be built on windows OS, linux, or just about any other OS including vendor unique ones. Because it only has to act as a file server, vendors can strip out other functions and optomize it for file sharing.

Not to confuse things too much but NAS devices also need to access disks just like servers do. In some cases the NAS device will use SAN technology to read and write to its disks. In this case the NAS device is sometimes called a NAS head. One side has ethernet over which NFS and CIFS communications travel and the back end connects to the fiber channel SAN over with the scsi commands travel as the NAS head reads and writes disk sectors.