[libvirt-users] lvm vs qcow (on NVMe)

[Stefan Hajnoczi]

On Thu, Nov 22, 2018 at 05:03:43PM +0100, Kashyap Chamarthy wrote:
> On Fri, Oct 26, 2018 at 12:32:48PM +0100, lejeczek wrote:
> > hi guys,
> > 
> > anybody observed, maybe has measured performance difference between
> > the two with qemu quests(windows OS)?
> > 
> > Any conclusions, recommendations?
> 
> [Cc Stefan from QEMU, probably he might have some pointers.]

You can get good performance with qcow2 if you preallocate the image
file:

  $ qemu-img create -f qcow2 -o preallocation=falloc vm001.qcow2 10G

Writing to new regions of the image has a higher cost without
preallocation.  The downside is that the storage will be reserved for
the disk image so you no longer start off with a tiny file that grows on
demand.  That's the trade-off if performance is critical.

Stefan
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 455 bytes
Desc: not available
URL: <http://listman.redhat.com/archives/libvirt-users/attachments/20181126/5628e81f/attachment.sig>