Re: shared disk (DOS)

[Tomas By]

On Sat, 10 Apr 2021 17:24:03 +0200, Peter Maydell wrote:
> If you are trying to have multiple guests running simultaneously
> which are all using the same disk, then that *is* a distributed
> filesystem setup (multiple clients, one disk).

Well...

"GlusterFS aggregates various storage servers over Ethernet or
Infiniband RDMA interconnect into one large parallel network file
system."

https://en.wikipedia.org/wiki/GlusterFS


> What that message
> is saying is effectively that you have two choices:
>  (1) [...]
>  (2) accept that you are running a multi-machine cluster which is
>      sharing a disk and use a filesystem type and guest setup that
>      works that way

Okay, #2 sounds fine...


> For DOS in particular, I don't expect it is likely to have support
> for multi-cluster disk use.

I'm not sure I follow the last bit there, but sharing a disk is what
SHARE.EXE is for:

"Locking files became necessary when MS-DOS began allowing files to be
accessed simultaneously by multiple programs, either through
multitasking or networking."

https://en.wikipedia.org/wiki/Share_(command)


> I suppose in theory you could set it up the way you'd have set up
> a shared disk in hardware back in the day: have a file server
> and get all the DOS guests to use it as a networked disk.

Well, you did not need a file server, only a network.

I think it worked the same on one single machine when Windows (or
OS/2) started to allow multi-tasking.

So how do I set this up under QEMU? Which format for the shared disk?

/Tomas