Windows cluster: disk use on both active and passive node

Hi all!

I have created a SQL cluster, following this guide:  http://pubs.vmware.com/vsphere-50/topic/com.vmware.ICbase/PDF/vsphere-esxi-vcenter-server-50-mscs-guide.pdf

The cluster is with two nodes (active/passive) on one host (cluster in a box) not using RDM.

My question is now: it looks like the disk I was given for this cluster (and some other servers) are almost full, since, according to vmware, both the passive and the active cluster node have allocated the cluster disks. As you might know, only the active cluster node are actually using the disks.

Is there a way to change this? Is this expected behaviour?

Please see picture:

Thanks in advance.