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The following table shows storage options and parameters for different hypervisors. VMware vSphere Citrix XenServer KVM Format for Disks, Templates, and Snapshots VMDK VHD QCOW2 iSCSI support VMFS Clustered LVM Yes, via Shared Mountpoint Fiber Channel support VMFS Yes, via Existing SR Yes, via Shared Mountpoint NFS support Y Y Y Local storage support Y Y Y Storage over-provisioning NFS and iSCSI NFS NFS XenServer uses a clustered LVM system to store VM images on iSCSI and Fiber Channel volumes and does not support over-provisioning in the hypervisor. The storage server itself, however, can support thin-provisioning. As a result the &PRODUCT; can still support storage over-provisioning by running on thin-provisioned storage volumes. KVM supports "Shared Mountpoint" storage. A shared mountpoint is a file system path local to each server in a given cluster. The path must be the same across all Hosts in the cluster, for example /mnt/primary1. This shared mountpoint is assumed to be a clustered filesystem such as OCFS2. In this case the &PRODUCT; does not attempt to mount or unmount the storage as is done with NFS. The &PRODUCT; requires that the administrator insure that the storage is available With NFS storage, &PRODUCT; manages the overprovisioning. In this case the global configuration parameter storage.overprovisioning.factor controls the degree of overprovisioning. This is independent of hypervisor type. Local storage is an option for primary storage for vSphere, XenServer, and KVM. When the local disk option is enabled, a local disk storage pool is automatically created on each host. To use local storage for the System Virtual Machines (such as the Virtual Router), set system.vm.use.local.storage to true in global configuration. &PRODUCT; supports multiple primary storage pools in a Cluster. For example, you could provision 2 NFS servers in primary storage. Or you could provision 1 iSCSI LUN initially and then add a second iSCSI LUN when the first approaches capacity.