[CentOS-devel] Cloud and VM Images

[Richard W.M. Jones]

On Sat, Jun 21, 2014 at 03:10:39AM +0100, Karanbir Singh wrote:
> hi,
> 
> I have just pushed a public build for a qcow2 image, this should be
> suiteable for any HVM environment. Please test as widely as possible.
> 
> http://buildlogs.centos.org/centos/7/cloud/

Is that built using the centos.sh script?

As a general comment, although not required, virt-builder would prefer
it if the image was xz-compressed.  The reason is that it has to
download the template and cache it in the user's $HOME, so a 960MB
template is obviously both slow to download and takes a lot of space.

NB: Don't bother with qcow2's internal compression feature.  It's a
waste of space.  xz is where it's at.

 - nearly best in class compression

 - real API (liblzma)

 - preserves sparseness, important for raw format images

 - virt-builder has a custom multithreaded unxz [1] -- it is
   sysconf(_SC_NPROCESSORS_ONLN) times faster than unxz

Rich.

[1] https://github.com/libguestfs/libguestfs/blob/master/builder/pxzcat-c.c

-- 
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