[pve-devel] [PATCH] qemu-img convert : use default cache=unsafe instead writeback

[Waschbüsch IT-Services GmbH]

> Am 01.08.2016 um 09:26 schrieb Dominik Csapak <d.csapak at proxmox.com>:
> 
> On 08/01/2016 08:51 AM, Alexandre Derumier wrote:
>> Signed-off-by: Alexandre Derumier <aderumier at odiso.com>
>> ---
>> PVE/QemuServer.pm | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
>> index 7778fb8..2414fd8 100644
>> --- a/PVE/QemuServer.pm
>> +++ b/PVE/QemuServer.pm
>> @@ -5605,7 +5605,7 @@ sub qemu_img_convert {
>> 	my $dst_path = PVE::Storage::path($storecfg, $dst_volid);
>> 
>> 	my $cmd = [];
>> -	push @$cmd, '/usr/bin/qemu-img', 'convert', '-t', 'writeback', '-p', '-n';
>> +	push @$cmd, '/usr/bin/qemu-img', 'convert', '-p', '-n';
>> 	push @$cmd, '-s', $snapname if($snapname && $src_format eq "qcow2");
>> 	push @$cmd, '-f', $src_format, '-O', $dst_format, $src_path;
>> 	if ($is_zero_initialized) {
>> 
> 
> is this really safe?
> 
> this also impacts cloning and the "move disk" function.
> what if i clone a vm to an nfs share and immediately move the vm to another host, then start it?

Also, when using move disk, will this make the 'Delete source' option potentially hazardous?
How do we determine that the disk has been completely and safely moved before removing the original?
I like performance improvements as much as the next guy, but I am sort of uneasy about this one.