Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements

From: Alex Bligh
Date: Thu Sep 15 2016 - 11:25:32 EST


> I doubt that qemu-nbd would ever want to support the situation with more
> than one client connection writing to the same image at the same time;
> the implications of sorting out data consistency between multiple
> writers is rather complex and not worth coding into qemu. So I think
> qemu would probably prefer to just prohibit the multiple writer
> situation.

Yeah, I was thinking about a 'no multiple connection' flag.

> And while multiple readers with no writer should be fine,
> I'm not even sure if multiple readers plus one writer can always be made
> to appear sane (if there is no coordination between the different
> connections, on an image where the writer changes AA to BA then flushes
> then changes to BB, it is still feasible that a reader could see AB
> (pre-flush state of the first sector, post-flush changes to the second
> sector, even though the writer never flushed that particular content to
> disk).


Alex Bligh

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