Hi, We're using Openstack Ironic to deploy baremetal servers. During the deployment process an agent (ironic-python-agent) running on Fedora linux uses qemu-img to write a qcow2 file to a blockdevice.
Recently we saw a change in behavior of qemu-img. Previously we were using Fedora 27 containing a fedora packaged version of qemu-img v2.10.2 (qemu-img-2.10.2-1.fc27.x86_64.rpm); now we use Fedora 29 containing a fedora packaged version of qemu-img v3.0.0 (qemu-img-3.0.0-2.fc29.x86_64.rpm). The command that is run by the ironic-python-agent (the same in both FC27 and FC29) is: qemu-img -t directsync -O host_device /tmp/image.qcow2 /dev/sda We observe that in Fedora 29 the qemu-img, before imaging the disk, it fully zeroes it. Taking into account the disk size, the whole process now takes 35 minutes instead of 50 seconds. This causes the ironic-python-agent operation to time-out. The Fedora 27 qemu-img doesn't do that. Scanning through the qemu-img source code, we found that adding -S 0 to the command on Fedora 29 qemu-img restores the behavior as observed in Fedora 27 qemu-img. Looking through the changelogs of qemu I couldn't find this behavior change documented. Now the questions: * Is this the expected/required behavior that qemu-img first zeroes the complete target disk before writing the image. In other words: is this a qemu-img bug? * Is applying the -S 0 parameter a safe/sound/sensible thing to do to revert to the old behavior. In other words: can I write a bug against the ironic-python-agent to start using this parameter? * If the behavior is expected: is there some pointer to documentation/changelogs I can read about this? Thanks, Regards, Fred De Backer SME Video Integration Engineer, IP/Optical Networks, Nokia fred.de_bac...@nokia.com Nokia Bell NV I Copernicuslaan 50, 2018 Antwerpen I BTW BE 0404 621 642 RPR Antwerpen I BNP Paribas Fortis 220-0002334-42 I IBAN BE 77 2200 0023 3442 I BIC GEBABEBB << This message (including any attachments) contains confidential information intended for a specific individual and purpose, and is protected by law. If you are not the intended recipient, you should delete this message. Any disclosure, copying, or distribution of this message, or the taking of any action based on it, is strictly prohibited without the prior consent of its author. >>
