[Coco] DriveWire netdisk interface

[John W. Linville]

On Thu, Nov 19, 2009 at 02:19:24PM -0500, Aaron Wolfe wrote:

> I wanted to use webdav, but as far as I could tell, webdav doesn't
> support reading or writing specific portions of a file.  If i'm wrong
> about that please let me know!

Hmmm, I wasn't aware of that -- FWIW I'm more of a kernel guy...

> To implement a disk image that "just works" with DECB and OS-9,
> we have to be able to read and write abitrary 256 byte sections of
> the file.  I wrote my own simple protocol for this because i didnt
> see any way to do this with http.

Well, I do appreciate that those semantics exist between the CoCo
and the DW server.  But I don't think those semantics really need to
exist between the DW server and the backing store.  In fact, those
semantics would seem to decrease overall performance and increase the
chance of disk image corruption in the event of a failure.

I guess what I was thinking is that you would use a pull/modify/push
model, where the pull would occur when the DW server "mounted" the
image and the push would occur when a dirty image was "unmounted".
If the webdav server is worth it's salt, that should at least ensure
that so long as the DW server didn't push a corrupted image then the
webdav server images should always be correct.

Now, pull/modify/push could slow down the mount/unmount process,
but realistically how big are those Internet-based CoCo disk images
going to be? :-)

John

P.S.  Again, I'm just trying to wise and helpful. :-)  Don't let me
discourage if you don't like my advice!
-- 
John W. Linville		Someday the world will need a hero, and you
linville at tuxdriver.com			might be all we have.  Be ready.