Software people won't like it but from a hardware perspective there is no reason two systems cannot have access to the same storage. If one only writes and one only reads there is no issue except trying to read from a file not yet complete. I am sure that can be resolved by simply waiting a prescribed amount of time before trying to read the file. If both systems want to read and write a simple semaphore can be created using files.
This would be a safe way to transfer data between systems. Unless the systems execute the files viruses on one system could not infect the other system. The infected file would be present but it would just be a file.
I have considered designing such a device myself but never seem to have the time. A development board with two USB slave ports (B) and one USB host port (A) could do it. Just pass all commands arriving on either slave port to the host port. Plug a USB drive or thumb drive into the host port. It wouldn't be quite that simple but that would be a starting point.
@kruug Storage that can be accessed from multiple machines in parallel is usually used with a http://en.wikipedia.org/wiki/Clustered_file_system. E.g. GFS or Lustre. I think all implementations require a communication channel separate from the storage itself, (usually IP over ethernet) for the hosts coordinate who's going to write where. Anyway, I doubt there are any multiple-writer USB storage devices, so this doesn't help :/ Clearly your Raspberry Pi is in need of Fibre Channel :P
– Peter Cordes – 2015-03-28T07:41:03.8073You'll need to explain precisely what you expect to accomplish to get a useful answer. – David Schwartz – 2013-06-07T12:14:19.970
Try a google search for "usb sharing" – Dave – 2013-06-07T12:30:19.797
1As @Ramhound stated, you can't have both computers access the USB Resource at the same time. For example, a USB hard drive can only be mounted on one computer at a time. A printer can only be available to one computer at a time. If you want/need access from both computers, you would have to set up a network share to do so. – Kruug – 2013-06-07T14:35:04.770
you could stick the usb device into a computer, like a mini or pico or nano itx then access it remotely. Make the computer as small as possible! – barlop – 2013-09-20T13:24:48.470
@barlop - What you describe is a network solution. The author specifically says this isn't an acceptable solution. – Ramhound – 2013-09-20T13:28:39.967