Re: [Qemu-devel] [PATCH] add file: migration support (r2)

[Jamie Lokier]

Paul Brook wrote:
> On Thursday 13 November 2008, Charles Duffy wrote:
> > This patch adds support for migration to and from file: targets, moves
> > common helpers between exec: and file: use cases from migration-exec.c
> > to migration.c, and adds a qemu_fdopen() helper parallel to qemu_fopen().
> >
> > Compared to the previous version submitted, it removes some cruft which
> > was accidentally included, and documents the limitations of O_NONBLOCK
> > on Linux with local filesystem access.
> 
> I don't see any documentation.
> 
> The documentation should make it clear that this is not intended as a 
> substitute for savvm/loadvm.

> A "live" migration doesn't make sense if you're writing to an actual
> file (rather than a FIFO) as you'll end up with unecessarily large
> files.

That's true.  It would be better to use a slightly different format
when writing to a file, which lays out the RAM linearly and overwrites
re-dirtied pages during the migration.

I'm not sure if "live" migration to a file is really useful.  "Dead"
migration is useful for suspending a VM to disk.

-- Jamie