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Network Attached Storage (NAS)
So What is NAS
In short Network Attached Storage is another server on the network in its own right and can in many cases, entirely replace a traditional file server with a Direct Attached Storage System (DAS) - especially if the server's only role has been to share files. If the NAS is to be used in addition to an existing server already being used to control users login and access permissions over data, such as in the case of a Windows 2003 server with Active Directory, then the NAS can integrate into the AD so that access permissions to the data on the Network Storage can still be controlled by the existing AD server / Domain Controller.
Network attached storage solves many of the problems associated with Directly Attached Storage by having much better connectivity - to the network this time and not directly to a server. By utilising a few commonly accepted networking file system standards (NFS or Network File System for the UNIX systems and CIFS or Common Internet File System, for the Windows family of operating systems); NAS devices are able to share data across networks covering almost every computer straight from the box.
The rise in NAS popularity has been largely helped by the increases in performance of the networks that distribute the data. Where as just a few years ago networks were limited by the 12.5MB/sec of a 10/100LAN, networks have now been given a new freedom, enjoying theoretical speeds of 125MB/sec with the gigabit (1GbE) Ethernets and for the fastest bandwidths available the new 10 Gig (10GbE) Ethernet cards and switches are now available and becomming slightly more affordable. With these advances in network technology, the network is no longer the bottleneck it once was and NAS is seen as a near ideal solution for many environments, enjoying four main benefits.
In Short a NAS system can be seen as another server on the main network that is capable of being connected to by many different types of client. It can administer its own security or usually also integrate with the Windows Active Directory to allow permissions to be set by the AD server.
It is different from a SAN in that a Storage Area Network usually has its own separate network for storage traffic and in that a SAN usually only serves its data to servers who then in turn make the data available to client machines.
It is different of course also to Direct Attached Storage also, since as the names suggest DAS is directly attached to a client or server whilst NAS is attached to the network.