> Oh, yes, there is no doubt that the result will be correct. My point is
> that people aren't usually interested so much in the physical layout of
> the clusters, but more about the fact that no metadata updates and no
> COW is necessary when you write to a cluster for the first time (i.e.
> becau
Am 13.05.2018 um 15:37 hat Ivan Ren geschrieben:
> > Doesn't this defeat the purpose of preallocation? Usually, the idea with
> > preallocation is that you don't need to update any metadata on the first
> > write, but if you set QCOW_OFLAG_ZERO, we do need a metadata update
> > again.
> >
> > So wh
> Doesn't this defeat the purpose of preallocation? Usually, the idea with
> preallocation is that you don't need to update any metadata on the first
> write, but if you set QCOW_OFLAG_ZERO, we do need a metadata update
> again.
>
> So what's the advantage compared to not preallocating at all?
Yes
Am 11.05.2018 um 17:36 hat Ivan Ren geschrieben:
> Create a qcow2 directly on bare block device with
> "-o preallocation=metadata" option. When read this qcow2, it will
> return pre-existing data on block device. This patch add
> QCOW_OFLAG_ZERO flag (supported in qcow_version >= 3) for
> prealloca
Create a qcow2 directly on bare block device with
"-o preallocation=metadata" option. When read this qcow2, it will
return pre-existing data on block device. This patch add
QCOW_OFLAG_ZERO flag (supported in qcow_version >= 3) for
preallocated l2 entry to avoid this problem.
Signed-off-by: Ivan Re
