On Thu, Dec 7, 2017 at 9:33 PM, Nir Soffer <nsoffer@redhat.com> wrote:
For transferring images over http, there is no way to avoid sending unused blocks, except compression.
OK, understood
Maybe this file was crated with preallocation=full?
In virt-manager there is not this logic by default. The default format is qcow2/sparse When you create/add a disk you can choose "Select or create custom storage": https://drive.google.com/file/d/1gAwjAG5aRFC5fFgkoZXT5wINvQnov 88p/view?usp=sharing
And then choose a format between: raw, qcow, qcow2, qed, vmdk, vpc, vdi
In my case it was the default one, so qcow2, as qemu-img correctly detects.
I tested creating qcow2 files with virt manager, and it seems to use the preallocation=metadata by default (behind your back), I guess for improving performance in some cases. oVirt doe not use this option so we don't have this issue when downloading files.
Ah, ok. I didn't know about this preallocation option of qemu-img Does your example mean that by default oVirt uses preallocation=off when creating thin provisoned disks?
I hope I convinced you this time ;-)
Nir
Yes :- ] and thanks for the deep an detailed explanation, Nir Thanks also to Eric for his comments in the other reply Gianluca