I did some undocumented testing to circle the issue down: It seems to affect Files that are stored as sparsed files either raw or qcow2.
There was a big event and I had the chance to find some people using glusterfs with qemu, too. the biggest difference as far as I could see was that they all where using xfs based backends while I am using ext4. I have to fix a few more issues in Production this week, then I will run more tests. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1793904 Title: files are randomly overwritten by Zero Bytes Status in QEMU: New Bug description: Hello together, I am currently tracking down a "Hard to reproduce" bug on my systems that I first discovered during gitlab installation: Here is the Text from the Gitlab Bug https://gitlab.com/gitlab-org/gitlab-ce/issues/51023 ---------------------------------------------------------------------------------------------- Steps to reproduce I still do not have all the steps together to reproduce, so far it is: apt install gitlab-ce and gitlab-rake backup:recovery Then it works for some time before it fails. What is the current bug behavior? I have a 12 hour old Installation of gitlab ce 11.2.3-ce.0 for debian stretch on a fresh debian stretch system together with our imported data. However it turns out that some gitlab related files contain Zero bytes instead of actual data. root@gitlab:~# xxd -l 16 /opt/gitlab/bin/gitlab-ctl 00000000: 0000 0000 0000 0000 0000 0000 0000 0000 ................ This behaviour is somewhat strange because it was working for a few minutes/hours. I did write a shell script to find out which files are affected of this memory loss. It turns out that only files located under /opt/gitlab are affected, if I rule out files like /var/log/faillog and some postgresql table files. What I find even stranger is that it does not seem to affect Logfiles/databases/git_repositorys but application files, like .rb scripts. and not all of them. No non gitlab package is affected. What is the expected correct behavior? Binarys and .rb files should stay as they are. Possible fixes I am still investigating, I hope that it is not an infrastructure problem (libvirt/qemu/glusterfs) it can still be one but the point that files of /opt/gitlab are affected and not any logfile and that we to not have similar problems with any other system leads me to the application for now. If I would have used docker the same problem might have caused a reboot of the container. But for the Debian package it is a bit of work to recover. That is all a workaround, however. --------------------------------------------------------------------------------------------- I do have found 2 more systems having the same problem with different software: root@erp:~# xxd -l 16 /usr/share/perl/5.26.2/constant.pm 00000000: 0000 0000 0000 0000 0000 0000 0000 0000 ................ The Filesize itself is, compared with another machine 00001660 Bytes for both the corrupted and the intact file. It looks to me from the outside that if some data in the qcow2 file is written too many bytes get written so it sometimes overwites data of existing files located right after the position in memory where the write goes to. I would like to rule out Linux+Ext4 filesystems because I find it highly unlikely that such an error keeps undiscovered in that part of the environment for long. I think the same might go for qemu. Which leaves qemu, gemu+gluster:// mount, qcow2 volumes, glusterfs, network. So I am now going to check if I can find any system which gets its volumes via fusermount instead of gluster:// path if the error is gone there. This may take a while. ----- some software versions--------------- QEMU emulator version 2.12.0 (Debian 1:2.12+dfsg-3) Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers libvirt-daemon-driver-storage-gluster/testing,unstable,now 4.6.0-2 amd64 [installed] ii glusterfs-client 4.1.3-1 amd64 To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1793904/+subscriptions
