[Qemu-devel] [Bug 1399191] Re: Large VHDX image size

[Max Reitz]

Hi Jan,

ls -l returns the length of the file; qemu-img info prints the size of
the file (just like du does). Those are not necessarily the same, as you
can see. On modern filesystems, files can have holes in them which do
contribute to the file length, but which do not use any space on disk
and thus do not contribute to file size.

Besides using qemu-img, you can obtain the actual disk usage (the file
size) by using du or ls --size (-s for short).

Max

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https://bugs.launchpad.net/bugs/1399191

Title:
  Large VHDX image size

Status in QEMU:
  New

Bug description:
  We are trying to convert a VMDK image to VHDX image for deploy to HyperV 
Server ( SCVMM 2012 SP1) using qemu-img.
  We tried converting the image using both 'fixed' as well as 'dynamic' format. 
We found that both the disks occupy the same size of 50GB. When the same is 
done with VHD image, we found that the dynamic disks are much lesser in size (5 
GB) than the fixed disk (50GB). 

  Why is that the VHDX generates large sized images for both the
  formats?

  The following commands were used to convert the vmdk image to VHDX
  format

  1. qemu-img convert -p -o subformat=fixed  -f vmdk -O vhdx Test.vmdk
  Test-fixed.vhdx

  qemu-img info Test-fixed.vhdx
  image: Test-fixed.vhdx
  file format: vhdx
  virtual size: 50G (53687091200 bytes)
  disk size: 50G
  cluster_size: 16777216


  
  2. qemu-img convert -p -o subformat=dynamic  -f vmdk -O vhdx Test.vmdk 
Test-dynamic.vhdx

  qemu-img info Test-dynamic.vhdx
  image: Test-dynamic.vhdx
  file format: vhdx
  virtual size: 50G (53687091200 bytes)
  disk size: 50G
  cluster_size: 16777216

  
  We tried this with the following version of qemu
  1. qemu-2.0.0
  2. qemu-2.1.2
  3. qemu-2.2.0-rc4

  
  Please let us know how to create compact VHDX images using qemu-img.
  Thank you

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