[Qemu-devel] [Bug 583296] Re: I/O errors with qemu-nbd/qcow2

[Shehbaz Jaffer]

Hi,

I tried this with qemu-img version 1.0, Ubuntu 12.04 host and gentoo guest, 
with qcow2 disk image. 
This seems to work fine. Perhaps it was fixed in the new qemu-img versions.

address@hidden:~$sudo dd if=/dev/nbd0 of=/dev/null bs=1M
8192+0 records in
8192+0 records out
8589934592 bytes (8.6 GB) copied, 185.003 s, 46.4 MB/s
address@hidden:~$

Did you try working with some other disk image? Did this issue get
resolved already? Perhaps more information will be required to debug
this now.

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https://bugs.launchpad.net/bugs/583296

Title:
  I/O errors with qemu-nbd/qcow2

Status in QEMU:
  New

Bug description:
  I tried to open a qcow2 file with qemu-nbd and backup the files in it.
  After some coping I get lot of I/O errors in dmesg and the system
  hangs. One time I got even a kernel panic (Of course on a productive
  Server ;-) )

  How to reproduce:
  1. Connect nbd to a qcow2 file, a virtual machine mustn't use this file:
  qemu-nbd --connect=/dev/nbd0 /mnt/qcow/andromeda.qcow2 
  2. Read some data from /dev/nbd0p1
  dd if=/dev/nbd0p1 of=/dev/null bs=1M

  After a few Seconds till Minutes somethings crash's

  Attached some dmesg logs

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