Building a reverse NAS (RNAS)
Posted by activemind on April 17, 2008
What the hell is this? Hold on let me explain and then maybe you can help me find a better term…or maybe something like this already exists and I just don’t know about it.
So what is a NAS (Network Attached Storage). It is a small device (like NSLU) or a enclosure (like Airlink ANAS 250) where it has a ethernet port and a USB port. You take a USB hardisk and plug it into the USB port. You take a ethernet cable and plug it into you router and Voila. Now you have a hard disk that can be accessed on your network.
So the basic philosophy is that the USB port expects a hard disk and the clients come from the ethernet side.
Well what I am looking for is something reverse of this.
Meaning, I want the USB port to “appear” as a hard disk and the ethernet port to provide the storage. So that I can plug the USB port into any device needing a USB hard disk and it will use my network storage as the storage.
Still doesn’t make sense.
Okay, let me give you an example. Take the case of a DVR/Tivo. So a DVR/Tivo records on a hard disk and some of the newer models allow you to use a external USB harddisk. But now if you want to view the recorded content on your PC you have to unplug the hard disk and plug it into your PC. Or if you have a networked home viewing system with a central server (one of these days I will write a post about my networked home video system…one of these days then its a pain because the content is on the hard disk in the other room but you want to watch it in this room….so either you get off your ass, unplug the hard disk, move the content to central server and then watch it, or you just watch something else. Most of the time it ends up being number 2 (at least in my case). But the problem arises when your kid wants to watch something you recorded and you want to watch something that coming live…guess what…you end up recording your live stuff and the kid gets to watch his recorded stuff. Now watching a recorded game when you already know the result is not too much fun…..
So now, if I have a device or enclosure or something that has a USB and a ethernet port, I can plug the USB into the DVR/Tivo. The device would make itself appear like a hard disk to the DVR/Tivo and use the ethernet to access the central sever for all its storage needs. Like a reverse of NAS. Meaning the storage is on ethernet port and USB port on the device appears like a hard disk.
Before embarking down road, I thought that there MUST be SOME device already out there that does jsut this. So I looked and one option came pretty close…but not that close. Airlink 101 has a hard disk enclosure which has ethernet and USB ports. So all good. You record via USB and access via ethernet from anywhere. Not that simple. It turns OFF The USB port as soon as you plug in the ethernet cable. I know it sucks!! All the required interfaces present, just some stupid firmware programmer decided he would not allow both the ports to be accessed at the same time because the company could save 10c by not putting the bus arbritation logic. Not trying to get too technical…but anyways…
So I think I have THE DEVICE in mind that I think can do this. Yes, same old NSLU.(on a sidenote, NSLU is one of the few gadgets where if you search for it, no where does the company’s name show up in the first couple of hits. Its a VERY popular device in the linux community but somehow Cisco does not seem to be too fond of this Linksys device after the buyout) It has all the needed ports and can run opensource Debian linux on it. Now I need to find the right s/w and packages to do this but I think its doable.
What da ya thunk?