[PATCH qemu-server] disk clone: warn when fallback is used instead of requested format

[PATCH qemu-server] disk clone: warn when fallback is used instead of requested format

[Maximiliano Sandoval]

We already print the same warning when importing. See f6039cedf for more
details.

Suggested-by: Shannon Sterz <s.sterz@proxmox.com>
Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>
---

Tested:
    On a LVM storage with savc enabled:
    
    $ qm disk move 100 scsi0 $storage --format vmdk
    
    which prints:
    
    format 'vmdk' is not supported by the target storage - using 'qcow2' instead

 src/PVE/QemuServer.pm | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
index 55e9f520..80d91a77 100644
--- a/src/PVE/QemuServer.pm
+++ b/src/PVE/QemuServer.pm
@@ -7936,6 +7936,8 @@ sub clone_disk {
         my $storeid = $storage || $src_storeid;
 
         my $dst_format = resolve_dst_disk_format($storecfg, $storeid, $drive->{file}, $format);
+        warn "format '$format' is not supported by the target storage - using '$dst_format' instead\n"
+            if $format && $format ne $dst_format;
 
         my $name = undef;
         my $size = undef;
-- 
2.47.3

Re: [PATCH qemu-server] disk clone: warn when fallback is used instead of requested format

[Shannon Sterz]

On Thu Jun 18, 2026 at 2:50 PM CEST, Maximiliano Sandoval wrote:
> We already print the same warning when importing. See f6039cedf for more
> details.
>
> Suggested-by: Shannon Sterz <s.sterz@proxmox.com>
> Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>
> ---
>
> Tested:
>     On a LVM storage with savc enabled:
>
>     $ qm disk move 100 scsi0 $storage --format vmdk
>
>     which prints:
>
>     format 'vmdk' is not supported by the target storage - using 'qcow2' instead
>
>  src/PVE/QemuServer.pm | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
> index 55e9f520..80d91a77 100644
> --- a/src/PVE/QemuServer.pm
> +++ b/src/PVE/QemuServer.pm
> @@ -7936,6 +7936,8 @@ sub clone_disk {
>          my $storeid = $storage || $src_storeid;
>
>          my $dst_format = resolve_dst_disk_format($storecfg, $storeid, $drive->{file}, $format);
> +        warn "format '$format' is not supported by the target storage - using '$dst_format' instead\n"
> +            if $format && $format ne $dst_format;
>
>          my $name = undef;
>          my $size = undef;

work as advertised, so consider this:

Tested-by: Shannon Sterz <s.sterz@proxmox.com>

note that we should probably still align the ui here though and only
allow formats supported by the storage. however, that should not block
this patch.