Hi,
On 2024-01-29 00:07, Francesco Poli wrote:
I was under the impression that the qcow2 format was the recommended
one for QEMU/KVM virtual machine images. At least, qemu-img(1)
describes it as "the most versatile format"...
Anyway, if you think that the raw format is a better choice for
autopkgtest and sbuild VM images, I take your word for it.
as I said in my other mail, I'm not the expert on the topic, so I asked
some experts. :)
In the other mail I already paraphrased what f_g said. I now also got
feedback from mjt (Michael Tokarev) our QEMU maintainer in Debian:
09:10 < mjt> for me, snapshots in qcow2 isn't of much use (I usually do
it the other way, by stacking another qcow2 on
top of the main image)
09:12 < jochensp> mjt: afair stacking only works if the base image is
already qcow2, or?
09:12 < mjt> speaking of qcow2 vs raw, both has their own good and bad
sides, mostly minor, and the preference is more
about taste than actual technical differences. People tend
to forget about sparseness of a raw image,
becoming surprizing the drivee usage increases dramatically
after a copy
09:13 < mjt> jochensp: no, stacking works on top of any image format
09:14 < mjt> ..on the other hand, trim support is more difficult on
qcow2
09:14 < mjt> myself, I choose raw for regular work and qcow2 when I have
to transfer the image somewhere
09:15 < mjt> it's quite easy to mount a qcow2 image on the host too, but
this needs extra layer (I usually use
qemu-nbd for this)
09:17 < mjt> for direct manipulation, when you have libext2fs and the
tools, raw is the only way to go
With that said, I think mmdebstrap-autopkgtest-build-qemu should keep
using raw images.
Thanks!
cheers, josch
