[comp.sys.ibm.pc.programmer] How do file servers work?

ts@cup.portal.com (Tim W Smith) (06/11/90)

How do file servers under DOS work?  That is, you've got these DOS
programs that are issuing INT 21h requests for file access, and
somehow these get translated into requests for files on a server.

Do the people that implement file servers just intercept all INT 21h
requests and process those that refer to the server, or is there a
better way?

How about things that are not file servers but have non-DOS file
systems, such as ISO 9660 CD-ROMs?

In general, what's the best way to make a non-DOS storage device
work under DOS, assuming that the file system format for the device
has already been defined and it is not a DOS file system, so you
can't just implement a block device driver for it?

						Tim Smith

silver@xrtll.uucp (Hi Ho Silver) (06/11/90)

In article <30686@cup.portal.com> ts@cup.portal.com (Tim W Smith) writes:
$Do the people that implement file servers just intercept all INT 21h
$requests and process those that refer to the server, or is there a
$better way?

   That's the way the all work, as far as I know.  Certainly that's how the
Novell system I'm running at work does it.  It isn't a terribly hard task,
it's just that there are a lot of calls you have to intercept and treat
separately.
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dixon@sagittarius.crd.ge.com (walt dixon) (06/11/90)

In <30686@cup.portal.com> Tim W Smith writes:

>How do file servers under DOS work?  That is, you've got these DOS
>programs that are issuing INT 21h requests for file access, and
>somehow these get translated into requests for files on a server.

>Do the people that implement file servers just intercept all INT 21h
>requests and process those that refer to the server, or is there a
>better way?

>How about things that are not file servers but have non-DOS file
>systems, such as ISO 9660 CD-ROMs?

>In general, what's the best way to make a non-DOS storage device
>work under DOS, assuming that the file system format for the device
>has already been defined and it is not a DOS file system, so you
>can't just implement a block device driver for it?

If one marks a logical drive as a network device,  DOS generates
int 2fh requests which can be mapped to another disk structure.
I'm not sure whether the format of these requests has been documented.
You might try looking on the interrupt list that Ralf Brown maintains.

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