Re: [Qemu-block] [Qemu-devel] [PATCH v2 0/3] block: Warn about usage of growing formats over non-growable protocols

[Paolo Bonzini]

On 06/05/2015 15:04, Max Reitz wrote:
>>
>> Introducing a warning for a normal QEMU invocation is a bit weird.
>>
>> What is the point of this series?  Were users confused that they hit
>> ENOSPC?
> 
> Users were confused when exporting a qcow2 image using nbd-server
> instead of qemu-img, and then accessing that NBD export with qemu
> (subsequently getting I/O errors on guest writes, if the image is not
> yet fully allocated): http://bugzilla.redhat.com/show_bug.cgi?id=1090713

I think NBD exports of non-raw images falls within the case of "user
should know what they're doing".  In particular, you don't even need
metadata preallocation, you just need a "truncate -s10G file.qcow2"
before invoking nbd-server.

So I think it's not worth fixing this, even though I see how it can be a
minor UI/UX issue.

Paolo