•Storage mode: supports Non-virtualization, Virtualization, and Raw device mapping modes.◾It takes time to create a common disk on a virtualized data store. However, a thin provisioning disk can be quickly created on a virtualized data store, taking the same time as a common disk on a non-virtualized data store takes. In addition, a thin provisioning disk supports advanced features that improve storage utilization and system security and reliability, such as thin provisioning, snapshots, and live storage migration. A common disk created on a non-virtualized data store has higher I/O performance than disks created on virtualized data stores but the common disk (except the one created on FusionStorage and advanced SAN storage as well as the local RAM disk) does not support advanced features. If Storage mode is set to Virtualization, you can set the data cluster size for the logical unit number (LUN) in Advanced. If a virtualized LUN is used, files are stored in noncontiguous data clusters on disks. A small data cluster offers high storage utilization but a low data reading rate.
◾In Raw device mapping mode, physical LUNs on SAN devices are directly attached to service VMs as disks to provide higher performance. Data stores in this mode are used as raw device mapped disks and cannot be divided. Therefore, the size of a disk created using the data store is the same as the data store size, and the disk does not support the advanced features. An RDM data store supports only VMs running certain OSs, such as Red Hat Linux Enterprise 5.4/5.5/6.1/6.2 64-bit. For details about the supported OS list, see the OS description for PVSCSI in the Compatibility.
http://support.huawei.com/hedex/pages/EDOC100007598531188559/05/EDOC100007598531188559/05/resources/05_fc/resource_mgt/it_58_57_000045.html?ft=0&fe=10&hib=4.3.5.1&id=it_58_57_000045_3&text=Adding%20a%20Data%20Store&docid=EDOC1000075985