I have multiple machines that must be removed from the corporate LAN because their OS is being retired. We run some specialized laboratory tasks (and hardware) on the "obsolete" machines that cannot easily migrate to the new LAN-compatible OS (Windows 7), so I am trying to find the simplest (and preferably cheapest) intermediate device that could satisfy the following performance requirements:

  1. Store ~1TB of data.

  2. Allow the obsolete machines to write to it without being on the corporate LAN.

  3. Be mapped as a network drive by Windows 7 machines that are on the corporate LAN.

My first thought was to set up a simple NAS drive, but the information that I have found on this subject suggests that NAS drives cannot also be written to locally (see Is there a NAS that can act as a "simple", "dumb" USB Drive? and One hard drive local to one computer but connected to server). However, those discussions don't appear entirely conclusive.

So question 1: can a NAS drive also be accessed locally while also being accessed via the network, or is this impossible?

Question 2: if not, what is the simplest solution? I can install another LAN-compatible PC to act as a server for a sub-LAN (?) to the "obsolete" machines -- but I was hoping to find a simpler solution. We have 6 non-co-located labs, so this seems a bit complicated.

Many thanks for any help!

  • Do the machines support VLANs? If they do just ask IT to create a VLAN for the legacy nodes. This keep the IT tasks with IT yet isolates the old OS nodes from the rest of the network. (If the old nodes OS is XP then this might be a challenge. XP does not support VLANs naively unless your network card and its driver does so). But I am hoping that they already consider Vista a legacy and that XP was dumped many seasons ago. – Hennes Oct 23 '13 at 19:15
  • Unfortunately, they are all XP machines. I will look into this, but the machines are likely all sporting a wide variety of network cards (and thus varying levels of VLAN support). – Mark Oct 23 '13 at 20:07

The simplest solution is a PC (running Linux/Samba or Windows) with two network cards, one on the corporate network and one networked to the lab equipment.

By using VLANs you could reduce this to one network card on the server (contrary to what Hennes says, you may put the lab boxes in their own VLAN, even if their OS does not support VLANs. OS-VLAN support is required only when a single NIC must talk to multiple VLANs, like your fileserver would be doing).

You cannot have USB-disk and network-disk access to the same device, because the USB computer expects to see a block of storage that it owns exclusively. It would then try to manage filesystem metadata, like directory entries and free blocks, with no clue that other systems are using (or changing!) the same data.

The lab computers therefore must use a storage protocol (such as CIFS or NFS or MTP-over-USB like another answer suggested) that allows for other clients to lock things and leaves the filesystem internals to a server.

  • Thanks Oh My Goodness -- any chance you have a take on Michael Suelmann's answer below? Do you know if MTP can circumvent the USB/network disk access conflict? – Mark Oct 23 '13 at 20:22
  • +1. I should have been more detailed in my comment. – Hennes Oct 23 '13 at 21:39
  • The three problems I see with MTP: (1) limited to one MTP client per NAS unless you find a NAS w/ multiple USB ports; (2) USB imposes physical constraints on where the server may be located; and (3) it won't appear as a filesystem to XP (or anything), you need "MTP initiator" software and (as you note), data generation and data sync will be separate operations. I'm sure it can work, but a NAS with 2 network ports (or VLAN support)/dual-homed PC is a more general solution that requires less engineering on the lab boxes and will probably adapt better to future requirements. – Oh My Goodness Oct 24 '13 at 0:04

As you found already, you cannot access a NAS in "dumb" USB drive mode and simultaneously from the network. What is possible is accessing a NAS via USB with the MTP protocol and via network. I've seen specs of NAS devices that support MTP. The question is if your legacy OS is supporting MTP protocol.

  • OK -- i just quickly read the wikipedia page on MTP; that sounds like it would work to sync lab-generated data (on XP boxes) to the NAS drive, which would then be accessible on the network. As far as I can tell, that meets all of my criteria. Am I missing something? – Mark Oct 23 '13 at 20:20

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