[libvirt-users] qemu-img convert to "sparse" LV

[Edoardo Comar]

Apologies as this is is not a specific libvirt question.

Is qemu-img convert compatible with thin-provisioned LVs as targets ?

I wanted to convert a file-based image to a LV image
where the file-based image has a capacity much larger than the actual data 
it contains, so it has a small footprint on disk
(either a qcow2 or a raw, but sparse, image).

If I use qemu-img convert -O raw ... with a target LV sized to the full 
capacity of the file-image, all is fine.

But if I try use an LV whose virtual size equals the capacity, but its 
size is smaller (although more than enough for the data) 
the LV is invariably corrupt.

If I try use a thin-provisioned LV pool, and a LV backed by that pool,
the LV resulting from qemu-img convert is not corrupt but it uses as much 
space as the file-image capacity it came from.

This on both RHEL64 and Fedora18.


--------------------------------------------------
regards,
Edoardo Comar
WebSphere Application Service Platform for Networks (ASPN)
ecomar at uk.ibm.com
+44 (0)1962 81 5576 
IBM UK Ltd, Hursley Park, SO21 2JN

Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number 
741598. 
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU