Re: [Users] re-thin a disk
On Wed, Mar 13, 2013 at 09:23:04PM +0000, Jonathan Horne wrote:
I have a virtual machine with a 500GB thin-provisioned disk, and on
it is about 2GB of data. Due to a pvmove operation I am running,
the 500GB disk with 2GB of data is growing and growing and is
currently 180GB in size, and im sure it will go all the way to the
500GB before it stops.
When this process is finished, is there a way to re-thin the disk
back down to the proper size again? What about the export/import
process? Would that export it to the data size, not the block size?
There's not a way to do this in-place currently, although we're
working on it.
If you can accept a copy, then 'qemu-img convert' will automatically
sparsify disks, although it only works if there is no left-over data
in the blocks.
Also requiring a copy, virt-sparsify can fully sparsify a disk even if
it has left-over but unused data blocks.
See also:
http://libguestfs.org/virt-sparsify.1.html
http://libguestfs.org/guestfs-faq.1.html#why-doesnt-virt-sparsify-work-on...
- - -
Your question also made me wonder if there was a tool to do an
in-place sparsification of a thin provisioned DM device, but there
doesn't seem to be anything for that. *If* such a tool did exist,
then you could use it in conjunction with the following guestfish
command:
http://libguestfs.org/guestfish.1.html#zero-free-space
ie. something like:
guestfish -a /dev/vg/guest
<fs> run
<fs> list-filesystems
# for each filesystem do:
<fs> mount /dev/XXX /
<fs> zero-free-space /
<fs> umount /
followed by running the non-existent thinning tool.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines. Boot with a
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