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Why are the qcow2 images compressed with xv instead of bzip2?

asked 2014-04-14 13:58:31 +0000

anonymous user


I had to look up unxv to decompress my Atomic host image, because I never see anything compressed with xv in the wild. Is there a technical reason they're distributed with xv compression instead of gzip, bzip2, or zip?

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answered 2014-07-23 17:37:42 +0000

paolo antinori gravatar image

standard zip support would useful for Vagrant workflows too:


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answered 2014-04-15 18:30:01 +0000

walters gravatar image

xz (LZMA) is a more efficient compression format than BZ2, and we assume that anyone who can use qcow2 disks has a Linux-based OS and can easily process xz files.

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This is pretty standard practice, yeah.

lzap ( 2014-04-15 20:39:27 +0000 )edit

Regardless of the quality of the compression, zip and tar.gz are really, really standard. For example, in the openstack instance I have access to, I can add a remote, compressed, qcow2 file, *if* it is in tar.gz or zip, but not xz. So, would you mind making a gzip'd version available?

langdon ( 2014-06-30 20:18:01 +0000 )edit

even Windows can make use of xz via 7zip. LZMA will soon replace bzip2 and tar.gz anyway..

merb ( 2014-12-12 11:18:59 +0000 )edit

answered 2014-04-17 18:03:41 +0000

DV gravatar image

my recollection is that libvirt has support for xz compression by default, I wonder if the decompression step is actually needed when importing from virt-manager

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Asked: 2014-04-14 13:58:31 +0000

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Last updated: Jul 23 '14