Hi there,
as always in life it´s very hard to make suggestions unless knowing what you really want.
What do you mean by "a shared disk between VMs" ?
Even more interesting what do you mean by "...to simulate a storage that will be used by 2 VMs in cluster" ?
Do you mean a shared storage visible to both VMs as guest in order to share data ?
Or do you talk about a shared storage (e.g. NFS) to store the VM images to start them from different nodes / hosts in the cluster ?
For the first one I would suggest to use SAMBA or NFS (which could provided by your host PC). Both VMs could then access the share to exchange data and you can simulate your later infrastructure.
In that case it would be neccessary you outline your later scenario in order to provide you more suggestions.
For the later one you can easily choosing a pre-configured solution.
FreeNAS is FreeBSD based and can be used to set up a NAS with FTP, iSCSI target, Samba, NFS within a few minutes:
http://www.freenas.org/
I´m using FreeNAS for a NFS-storage for three XenServer hosts in my company.
A Linux based alternative is OpenFiler:
http://www.openfiler.com/community/download/
so what are you looking for ?
