-Say for instance you create a VM with a 32GB hard disk, and after installing the
-guest system OS, the root filesystem of the VM contains 3 GB of data.
-In that case only 3GB are written to the storage, even if the guest VM sees a
-32GB hard drive. In this way thin provisioning allows you to create disk images
-which are larger than the currently available storage blocks. You can create
-large disk images for your VMs, and when the need arises, add more disks to your
-storage without resizing the VMs filesystems.
+A number of storages, and the Qemu image format `qcow2`, support 'thin
+provisioning'. With thin provisioning activated, only the blocks that
+the guest system actually use will be written to the storage.
+
+Say for instance you create a VM with a 32GB hard disk, and after
+installing the guest system OS, the root file system of the VM contains
+3 GB of data. In that case only 3GB are written to the storage, even
+if the guest VM sees a 32GB hard drive. In this way thin provisioning
+allows you to create disk images which are larger than the currently
+available storage blocks. You can create large disk images for your
+VMs, and when the need arises, add more disks to your storage without
+resizing the VMs' file systems.
+
+All storage types which have the ``Snapshots'' feature also support thin
+provisioning.
+
+CAUTION: If a storage runs full, all guests using volumes on that
+storage receives IO error. This can cause file system inconsistencies
+and may corrupt your data. So it is advisable to avoid
+over-provisioning of your storage resources, or carefully observe
+free space to avoid such conditions.