Controllers; Storage Systems; Channels; Disk Drives - Adaptec DuraStor 7220SS User Manual

Storage Concepts

Controllers

A controller is a hardware device that performs input/output (I/O)
functions. Controllers also perform other functions such as read
and write caching and RAID management. They can be internal
(inside the host computer) or external (in an enclosure). Controllers
are also known as an adapters, embedded storage controllers, or
Host Bus Adapters (HBA).

Storage Systems

A storage system exists when the RAID controller resides outside of
the server enclosure. The storage system is controlled from the host
system using storage manager software such as Disk Array
Administrator. Since the controller is located in an external
enclosure and accessed using standard SCSI protocols, the need for
specific operating system drivers is eliminated. Some external
RAID controllers can be configured with single or dual host
channels and can support either standalone mode, or an active-
active failover pair.

Channels

A channel is any path used for the transfer of data and control
information between storage devices and the controller or storage
system. Each controller's channel is identified by a number. A
channel is also known as a bus.

Disk Drives

The term disk drive refers to the physical disk devices that store
your data. Depending on your controller, you may use either SCSI
or ATA drives.
A SCSI drive is identified by a disk ID, which is displayed in the
following format:
2:04:0
Logical Unit Number (LUN)
Channel Number SCSI ID
A-2