In new installations, several new partitions are created for the boot banks, the scratch partition, and the locker. New ESXi 5.x installations use GUID Partition Tables (GPT) instead of MSDOS-based partitioning.
The partition table is fixed as part of the binary image, and is written to the disk at the time the system is installed. The ESXi installer leaves the scratch and VMFS partitions blank, and ESXi creates them when the host is rebooted for the first time after installation or upgrade. The scratch partition is 4GB. The rest of the disk is formatted as a VMFS5 partition.