I haven't tried all of your combinations, but when I mount a second disk using the growpart/e2fsck/resize2fs sequence that you suggest and then mount it, it grows to 725 MB and then zerofree reports what you observed:
Both virtual disks are ubuntu 20.04 cloudimgs extended to 25 GB. I used the procedure I described on May 20 (cloudinit.iso on a virtual CD-ROM) with the one disk as root and the other one as /dev/sdb. Both were identical when I booted the VM.
You mentioned that "all tools that make it easy for me to deploy one also pick virtio by default"; can you run qemu from the command line on a bare metal system? If so, I thought my May 20 procedure was pretty simple. If not, then I guess it's harder to verify this.
@Christian,
I haven't tried all of your combinations, but when I mount a second disk using the growpart/ e2fsck/ resize2fs sequence that you suggest and then mount it, it grows to 725 MB and then zerofree reports what you observed:
baccala@ osito:~ /NPDC/GNS3/ bug$ sudo zerofree -v /dev/nbd0p1
3/5963617/6525179
But when I use an identical disk as the root filesystem, it grows to 789 MB and then zerofree reports this:
baccala@ osito:~ /NPDC/GNS3/ bug$ sudo zerofree -v /dev/nbd0p1 6525179
1524/5953550/
Both virtual disks are ubuntu 20.04 cloudimgs extended to 25 GB. I used the procedure I described on May 20 (cloudinit.iso on a virtual CD-ROM) with the one disk as root and the other one as /dev/sdb. Both were identical when I booted the VM.
You mentioned that "all tools that make it easy for me to deploy one also pick virtio by default"; can you run qemu from the command line on a bare metal system? If so, I thought my May 20 procedure was pretty simple. If not, then I guess it's harder to verify this.