and devices.The logical unit numbers were introduced because SCSI
only has a limited number ofidentification numbers
available to address the system components such as thedisk arrays
. Each SCSI device has at least one, up to a maximum of eight LUNs. The logical unit number is assigned by the host when it detects an attached SCSI device. The Logicl Unit Number is used to identify the Logical Units (LU) for the SCSI bus. Such a logical unit can be a storage array or part of a storage array, such as a hard disk drive (HD) or solid-state drive (SSD). Even a single partition can represent a Logical Unit and be identified with a Logical Unit Number.