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

[Stefan Hajnoczi]

On Thu, Mar 19, 2015 at 03:03:18PM -0400, Max Reitz wrote:
> Some image formats (e.g. qcow2) require the underlying file to grow on
> write accesses, but this is in fact not supported by all protocols (e.g.
> nbd does not). If such a format requiring file growth is used
> non-read-only over a protocol which does not support this, a warning
> should be issued.
> 
> This warning is issued for example whenever one tries to export a qcow2
> image over nbd-server and use the export from qemu.

The warning implies that the user should switch to read-only or a
different protocol, but this configuration is perfectly normal.  For
example, oVirt uses qcow2 on LVM volumes.

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?

Stefan

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