Starting an ESXi installation that is a part of a vSAN cluster from a flash device imposes certain restrictions.

When you boot a vSAN host from a USB/SD device, you must use a high-quality USB or SD flash drive of 4 GB or larger.

When you boot a vSAN host from a SATADOM device, you must use single-level cell (SLC) device. The size of the boot device must be at least 16 GB.

During installation, the ESXi installer creates a coredump partition on the boot device. The default size of the coredump partition satisfies most installation requirements. (You need to configure the core dump partition)

• If the memory of the ESXi host has 512 GB of memory or less, you can boot the host from a USB, SD, or SATADOM device.

• If the memory of the ESXi host has more than 512 GB, consider the following guidelines.

  • You can boot the host from a SATADOM or disk device with a size of at least 16 GB. When you use a SATADOM device, use a single-level cell (SLC) device.

  • If you are using vSAN 6.5 or later, you must resize the coredump partition on ESXi hosts to boot from USB/SD devices. For more information, see the VMware knowledge base article at http://kb.vmware.com/kb/2147881.

Hosts that boot from a disk have a local VMFS. If you have a disk with VMFS that runs VMs, you must separate the disk for an ESXi boot that is not for vSAN. In this case you need separate controllers.