There seems to be some confusion regarding the partitions and RAID volumes. With ESXi versions prior to ESXi 5, an installation/reinstallation always formatted the whole installation disk/volume, disregarding whether or not this contained a VMFS partition (datastore). So it was a good idea to split the RAID into several logical volumes (e.g. 10GB for the ESXi installation) to be able to reinstall if required, With ESXi 5 things changed and the installation offers the option to preserve an existing datastore, so there's no more need to split the RAID.
Another reason to split the RAID into multiple logical volumes was the fact that previous versions of ESXi only supported LUNs with up to ~2TB, ESXi 5 supports ~64TB (except for some HP Smartarray RAID controllers).
André
Message was edited by: a.p.