On Mon, 2009-10-19 at 09:27 -0400, M. Adam Davis wrote:
> As David pointed out, once you plug the mass storage device in, the
> computer expects the file system to remain static.

> However, it's worth trying out, to see how each OS handles a mass
> storage interface that changes.  Go ahead and make the MSD device, and
> have a 'virtual' file on there.  The file contents will be derived
> from, perhaps, an internal running counter, and will be fed to the
> computer whenever it requests that particular block of information.
> 
> See if reloading the file requests the data again.  There may also be
> some settings in the USB mass storage class that force the computer to
> not cache information (useful for security reasons).  You may also
> have the option of setting up the cache timing - making it so it won't
> delay file system writes, for instance.  Then you could use javascript
> to change files on the device, which would allow a two-way mass file
> system interface. (There is a USB wiki that does this - no need for a
> server or software to edit files).

I've done something very similar. It can be made to work, but there are
many issues as you describe.

In my case I had to have the "files" be big enough so that they wouldn't
fit in the OS's cache, in my case my "file" was 2GB so to avoid cache
issues I read the whole file each time. Sounds like that wouldn't be to
useful but for the functionality I needed it actually worked very well!

I did eventually find a way to cause the OS (Linux) to flush it's disk
cache, that let me read smaller files.

TTYL

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