A virtual machine uses a virtual disk to store its operating system, program files, and other data associated with its activities. A virtual disk is a large physical file, or a set of files, that can be copied, moved, archived, and backed up.
To store virtual disk files and manipulate the files, a host requires dedicated storage space. ESXi storage is storage space on a variety of physical storage systems, local or networked, that a host uses to store virtual machine disks.
Managing iSCSI Storage discusses iSCSI storage management. Managing Third-Party Storage Arrays explains how to manage the Pluggable Storage Architecture, including Path Selection Plugin (PSP) and Storage Array Type Plug-in (SATP) configuration.
For information on masking and unmasking paths with ESXCLI, see the vSphere Storage documentation.