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Other than the type of box it's in, I really don't understand the difference.
2011-07-03 18:52:00
An external hard disk can only be connected to one PC at a time. An NAS is connected to the network, and can therefore be accessed by hundreds of devices simultaneously. An NAS also generally has an OS built into it and additionality functionality not available in an external drive, such as streaming movie player, printer sharing, or remote access over the internet. In fact, an external hard disk is no different to an internal one. the box it's in simply provides power, and changes the SATA /IDE interface to a USB. No additional functionality or brains in there.
2011-07-03 19:52:00
Thank you James.I assume then, that the NAS OS is there mainly to take some stress off of the accessing PCs, is this correct?
2011-07-03 23:19:00
It's more like a very low profile computer with a stripped down OS (mostly some Linux). The OS is there manage the storage (Partitions, File System), to provide network connectivity (TCP/IP, settings etc.) and services (SMB, AFP, ...). Without those it wouldn't be possible to access the device.It's not about taking stress off the accessing device. No matter if the storage is NAS, SAN or DAS (direct attached storage via USB/FW/eSATA) using the storage will result in activity (as in used resources) on the computer.In general you can say that an external Hard Drive is really just an Hard Drive with a converter to one of the external interfaces (USB, Firewire, eSATA) while a NAS is a special form factor of a server with a certain set of functionality.The only storage that sits in between would be NDAS (Network Direct Attached Storage). You can see it as a server-less network attached Hard Drive. It also doesn't use TCP/IP but the LPX protocol for access.