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[Qemu-devel] [Bug 1793904] Re: files are randomly overwritten by Zero By

From: Hans
Subject: [Qemu-devel] [Bug 1793904] Re: files are randomly overwritten by Zero Bytes
Date: Wed, 26 Sep 2018 22:07:48 -0000

Hi John,

As for your second question: 
ii  glusterfs-comm 4.1.3-1      amd64        GlusterFS common libraries and tr

As for the other parts:  I was playing with this one ealier, therefore this is 
not completely relieable: 

qemu-img check images/conesphere_internet_meeting1.qcow2 
No errors were found on the image.
143086/491520 = 29.11% allocated, 7.72% fragmented, 0.00% compressed clusters
Image end offset: 9379708928

I will try to reproduce  your Ideas as soon as I can. :)

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  files are randomly overwritten by Zero Bytes

Status in QEMU:

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 

  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.

  address@hidden:~# 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

  address@hidden:~# 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

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