NAS Architecture File I/O File System Block I/O LAN NAS Appliance
File based Storage Connectivity File system resides in NAS Device IP Connectivity
Server / Workstation
This diagram shows how the NAS takes responsibility for managing and organising the stored data from the application server. The NAS appliance is not just a storage device directly connected to the LAN – it does in fact have an optimised server contained within it. This server (sometimes referred to as a ‘NAS Head’) normally runs a cut down, optimised operating system which communicates with the other servers over the LAN and manages the data storage subsystem in the NAS Appliance. All communication with the data storage devices inside the NAS appliance is via the NAS Head. It can exhibit the same characteristics as when accessing DAS over the LAN – a potential bottleneck in the NAS Head is the downside – but by offloading the data management and organization functions, the NAS Head can allow the application server to release more computing power to the application it is running. One major difference between scaling storage with NAS rather than DAS is that the when a NAS is added there is no need for a new operating system licence for each user – whereas if a server is added to scale a DAS environment – potentially requiring a new licence for each user.