Re: shared disk (DOS)

[Tomas By]

On Mon, 12 Apr 2021 11:16:21 +0200, Peter Maydell wrote:
> No, that doesn't work. QEMU doesn't "see" filesystem formats at all.
> To QEMU, a disk is simply a big bag of bytes. It can have anything
> on it that the guest wants, and it's up to the guest how it interprets
> it: QEMU just provides the functionality for "read some bytes"
> and "write some bytes". Whether the disk has a FAT filesystem on it
> or something else is up to the guest. (This is exactly the same way
> that a real hard disk can have anything on it, and the disk itself
> has no knowledge about the format.)


Well... I have problems getting all this to fit together logically.

Why then is there a difference (according to page linked earlier)
between raw and ocr2/gfs?

The point is not how qemu sees the bits, but how it handles concurrent
access from multiple instances.

Raw, as I understand it, just makes the first instance have exclusive
access and treats the whole disk as one unit. I was hoping there would
be some other system with more discriminiation.

I don't see why this should not work. Qemu divides the disk into a
bunch of pieces, no matter how, and the instances each have (more or
less) random access.

/Tomas