[Qemu-devel] [Bug 814222] Re: kvm cannot use vhd files over 127GB

[Launchpad Bug Tracker]

This bug was fixed in the package qemu-kvm - 0.14.1+noroms-0ubuntu5

---------------
qemu-kvm (0.14.1+noroms-0ubuntu5) oneiric; urgency=low

  * debian/patches/vpc.patch: detect vpc files which are too big
    (LP: #814222)
 -- Serge Hallyn <address@hidden>   Mon, 12 Sep 2011 11:28:36 -0500

** Changed in: qemu-kvm (Ubuntu)
       Status: Triaged => Fix Released

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/814222

Title:
  kvm cannot use vhd files over 127GB

Status in QEMU:
  New
Status in “qemu-kvm” package in Ubuntu:
  Fix Released

Bug description:
  The primary use case for using vhds with KVM is to perform a
  conversion to a raw image file so that one could move from Hyper-V to
  Linux-KVM.  See more on this http://blog.allanglesit.com/2011/03
  /linux-kvm-migrating-hyper-v-vhd-images-to-kvm/

  # kvm-img convert -f raw -O vpc /root/file.vhd /root/file.img

  The above works great if you have VHDs smaller than 127GB, however if
  it is larger, then no error is generated during the conversion
  process, but it appears to just process up to that 127GB barrier and
  no more.  Also of note.  VHDs can also be run directly using KVM if
  they are smaller than 127GB.  VHDs can be read and function well using
  virtualbox as well as hyper-v, so I suspect the problem lies not with
  the VHD format (since that has a 2TB limitation).  But instead with
  how qemu-kvm is interpreting them.

  BORING VERSION INFO:
  # cat /etc/issue
  Ubuntu 11.04 \n \l
  # uname -rmiv
  2.6.38-8-server #42-Ubuntu SMP Mon Apr 11 03:49:04 UTC 2011 x86_64 x86_64
  # apt-cache policy kvm
  kvm:
    Installed: 1:84+dfsg-0ubuntu16+0.14.0+noroms+0ubuntu4.1
    Candidate: 1:84+dfsg-0ubuntu16+0.14.0+noroms+0ubuntu4.1
    Version table:
   *** 1:84+dfsg-0ubuntu16+0.14.0+noroms+0ubuntu4.1 0
          500 http://apt.sonosite.com/ubuntu/ natty-updates/main amd64 Packages
          500 http://apt.sonosite.com/ubuntu/ natty-security/main amd64 Packages
          100 /var/lib/dpkg/status
       1:84+dfsg-0ubuntu16+0.14.0+noroms+0ubuntu4 0
          500 http://apt.sonosite.com/ubuntu/ natty/main amd64 Packages
  # apt-cache policy libvirt-bin
  libvirt-bin:
    Installed: 0.8.8-1ubuntu6.2
    Candidate: 0.8.8-1ubuntu6.2
    Version table:
   *** 0.8.8-1ubuntu6.2 0
          500 http://apt.sonosite.com/ubuntu/ natty-updates/main amd64 Packages
          500 http://apt.sonosite.com/ubuntu/ natty-security/main amd64 Packages
          100 /var/lib/dpkg/status
       0.8.8-1ubuntu6 0
          500 http://apt.sonosite.com/ubuntu/ natty/main amd64 Packages

  qemu-img version 0.14.0

  # vboxmanage -v
  4.0.12r72916

  
  REPRODUCTION STEPS (requires Windows 7 or Windows 2008 R2 with < 1GB of free 
space)

  ##  WINDOWS  MACHINE  ##

  Use Computer Management > Disk Management
  -Create 2 VHD files, both dynamically expanding 120GB and 140GB respectively.
  -Do not initialize  or format.

  These files will need to be transferred to an Ubuntu KVM machine (pscp
  is what I used but usb would work as well).

  ##  UBUNTU KVM MACHINE  ##

  # ls *.vhd
  120g-dyn.vhd  140g-dyn.vhd
  # kvm-img info 120g-dyn.vhd 
  image: 120g-dyn.vhd
  file format: vpc
  virtual size: 120G (128847052800 bytes)
  disk size: 244K
  # kvm-img info 140g-dyn.vhd 
  image: 140g-dyn.vhd
  file format: vpc
  virtual size: 127G (136899993600 bytes)
  disk size: 284K
  # kvm-img info 120g-dyn.vhd | grep "virtual size"
  virtual size: 120G (128847052800 bytes)
  # kvm-img info 140g-dyn.vhd | grep "virtual size"
  virtual size: 127G (136899993600 bytes)

  Regardless of how big the second vhd is I always get a virtual size of
  127G

  Now if we use virtualbox to view the vhds we see markedly different
  results.

  # VBoxManage showhdinfo 120g-dyn.vhd
  UUID:                 e63681e0-ff12-4114-85de-7d13562b36db
  Accessible:           yes
  Logical size:         122880 MBytes
  Current size on disk: 0 MBytes
  Type:                 normal (base)
  Storage format:       VHD
  Format variant:       dynamic default
  Location:             /root/120g-dyn.vhd
  # VBoxManage showhdinfo 140g-dyn.vhd 
  UUID:                 94531905-46b4-469f-bb44-7a7d388fb38f
  Accessible:           yes
  Logical size:         143360 MBytes
  Current size on disk: 0 MBytes
  Type:                 normal (base)
  Storage format:       VHD
  Format variant:       dynamic default
  Location:             /root/140g-dyn.vhd

  # kvm-img convert -f vpc -O raw 120g-dyn.vhd 120g-dyn.img
  #
  # kvm-img convert -f vpc -O raw 140g-dyn.vhd 140g-dyn.img
  #

  # kvm-img info 120g-dyn.img 
  image: 120g-dyn.img
  file format: raw
  virtual size: 120G (128847052800 bytes)
  disk size: 0
  # kvm-img info 120g-dyn.img | grep "virtual size"
  virtual size: 120G (128847052800 bytes)
  # kvm-img info 140g-dyn.img 
  image: 140g-dyn.img
  file format: raw
  virtual size: 127G (136899993600 bytes)
  disk size: 0
  # kvm-img info 140g-dyn.img | grep "virtual size"
  virtual size: 127G (136899993600 bytes)

  Notice after the conversion the raw image will the taken on the
  partial geometry of the vhd, thus rendering that image invalid.

  vboxmanage has a clonehd option which allows you to successfully
  convert vhd to a raw image, which kvm then sees properly.

  For giggles I also tested with a 140GB fixed VHD (in the same manner
  as above) and it displayed the virtual size as correct, so a good work
  around is to convert your VHDs to fixed, then use kvm-img to convert
  them.

  Keep in mind that these reproduction steps will not have a file
  systems therefore no valid data, if there were for example NTFS with a
  text file the problem would still occur but more importantly the guest
  trying to use it would not be able to open the disk because of it
  being unable to find the final sector.

  So long story short I think we are dealing with 2 issues here.

  1) kvm not being able to deal with dynamic VHD files larger than 127GB
  2) kvm-img not generating an error when it "fails" at converting or 
displaying information on dynamic VHDs larger than 127GB.  The error should be 
something like "qemu-kvm does not support dynamic VHD files larger that 
127GB..."

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/814222/+subscriptions