On Wed, Jun 25, 2025 at 7:04 AM lejeczek via Discuss < discuss@lists.centos.org> wrote:

hi guys. I have two virtually identical hardware boxes which report qcow2 sizes differently:

-> $ du -xh /00-VMsy//enc.vdb.back1.proxmox.qcow2 2.9G /00-VMsy//enc.vdb.back1.proxmox.qcow2

-> $ du -xh /00-VMsy//enc.vdb.back1.proxmox.qcow2 71G /00-VMsy//enc.vdb.back1.proxmox.qcow2

I checked I though obvious places: ext4 header shows the same features, I also looked at NVMes which all are formated with the same block size, mountpoins mount the same way. But, I must be still missing something... trivial? I'm thinking - perhaps some kernel tunables - but if so, which ones I cannot find. 'ls' reports the same everywhere, virtual 71G size. (so with spares) All thoughts shared are much appreciated. thanks, L.

This looks like a sparse file issue, something I hit often when creating a qcow, and then copy/sync it to another. Most likely the smaller file was the original, sparse file, and then it was copied with regular cp or rsync without --sparse.

I usually use 'rsync --sparse ...' even when copying locally. But I wouldn't be surprised if there was a better way of copying sparse files.

Troy