Now that you have seen how to use Cinder, you may be wondering where that volume that was created was stored. The cloud may be a facade of endless resources, but the reality is that there are actual physical resources that have to back the virtual resources of the cloud. By default, Cinder is configured to use LVM as its backing store. Packstack will look for a volume group named cinder-volumes configured on the node running the cinder-volume service. If one does not exist, Packstack will create a virtual disk and mount it as a loopback device to use as the physical volume to create a cinder-volumes volume group. The volume you just created was a logical volume in the cinder-volumes volume group. This is not an ideal place to store a virtual storage resource for anything more than a demonstration. Using a virtual disk mounted as a loopback device has very poor performance and will quickly become a bottleneck under load.

If there is a cinder-volumes group, then Packstack will...