Re: [Qemu-devel] qemu-img problem when create a file larger than fs's size

[Stefan Hajnoczi]

On Wed, May 08, 2013 at 01:18:17PM +0800, yuxh wrote:
> I have to consult you a qemu-img's problem.
> 
> Is this reasonable to create a file which is larger than the
> available size of the fs by qemu-img cmd ?
> 
> When I use qemu-img create a file which is larger than the available
> size of the fs, the creation is completed succesfully.
> 
> However when I use this file in guest as a guest's disk, and write
> beyond the size the host file can provides, the guest was paused by
> qemu-kvm or libvirt and was in maybe a infinite circle where the
> guest just can't be used except I detach the disk from guest or
> destroy the guest.

You can change the ENOSPC policy with -drive werror=,rerror=.  See the
QEMU man page.

The default behavior is to pause the guest so the host admin can free up
or add space.  Then the guest can be continued - this will retry the
I/O.

But you can also tell QEMU to pass the error through to the guest using
the -drive werror=,rerror= options.

Stefan