When you start ESXi, the host enters an autoconfiguration phase during which system storage devices are configured with defaults.

When you reboot the ESXi host after installing the ESXi image, the host configures the system storage devices with default settings. By default, all visible blank internal disks are formatted with VMFS, so you can store virtual machines on the disks. In ESXi Embedded, all visible blank internal disks with VMFS are also formatted by default.

Caution:

ESXi overwrites any disks that appear to be blank. Disks are considered to be blank if they do not have a valid partition table or partitions. If you are using software that uses such disks, in particular if you are using logical volume manager (LVM) instead of, or in addition to, conventional partitioning schemes, ESXi might cause local LVM to be reformatted. Back up your system data before you power on ESXi for the first time.

On the hard drive or USB device that the ESXi host is booting from, the disk-formatting software retains existing diagnostic partitions that the hardware vendor creates. In the remaining space, the software creates the partitions described in 1.

Table 1. Partitions Created by ESXi on the Host Drive

ESXi Version

Partitions Created

ESXi Installable

For fresh installations, several new partitions are created for the boot banks, the scratch partition, and the locker. Fresh ESXi installations use GUID Partition Tables (GPT) instead of MSDOS-based partitioning. The partition table itself 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. One 4GB VFAT scratch partition is created for system swap. See About the Scratch Partition. The VFAT scratch partition is created only on the disk from which the ESXi host is booting.

Note:

To create the VMFS volume and a scratch partition with the installation, the ESXi installer requires a minimum of 5.2GB of free space on the installation disk.

The installer affects only the installation disk. The installer does not affect other disks of the server. When you install on a disk, the installer overwrites the entire disk. When the installer autoconfigures storage, the installer does not overwrite hardware vendor partitions. During ESXi installation, the installer creates a 110MB diagnostic partition for core dumps.

ESXi Embedded

One 110MB diagnostic partition for core dumps, if this partition is not present on another disk. The VFAT scratch and diagnostic partitions are created only on the disk from which the ESXi host is booting. On other disks, the software creates one VMFS5 partition per blank disk, using the whole disk. Only blank disks are formatted.

Both ESXi Installable and ESXi Embedded

One VMFS5 partition on the remaining free space.

You might want to override this default behavior if, for example, you use shared storage devices instead of local storage. To prevent automatic disk formatting, detach the local storage devices from the host under the following circumstances:

  • Before you start the host for the first time.

  • Before you start the host after you reset the host to the configuration defaults.

To override the VMFS formatting if automatic disk formatting already occurred, you can remove the datastore. See the vCenter Server and Host Management documentation.