How are new LUNs discovered by an ESX Host?

A.
A rescan operation is required every time a new LUN is added

B.
A reboot operation is required to detect newly presented LUNs

C.
ESX Server automatically detects new LUNs as they are presented

D.
ESX Server periodically performs a rescan operation to detect any new LUNs

Explanation:
iSCSI SAN Configuration Guide, page 26.
The VMkernel discovers LUNs when it boots, and those LUNs are then visible in the
vSphere Client. If changes are made to the LUNs, you must rescan to see those changes.
New LUNs created on the iSCSI storage
Changes to LUN access control
Changes in connectivity