1.2.2.1 Mass Storage Devices and Controllers
Mass storage devices record data on magnetic media. The data is not lost when
you turn off the system, but it can be altered or erased if you record over the
data. Use mass storage devices to store data and software permanently. When
the data or software is needed, the CPU copies it from the mass storage device
into main memory.
The two primary types of mass storage devices are the integrated storage
elements and devices with removable media such as tape cartridges and compact
disks.
Integrated Storage Elements (ISEs)
Up to seven EF/RF-series ISEs can be installed in your system (using the
dual-disk RFxx). An ISE is an intelligent storage device that contains its own
controller and server. Special mounting hardware lets the device plug directly
into the system backplane.
Devices with Removable Media
Devices with removable media, such as tape cartridges, are used as both input
and output devices. In addition, compact optical disks are used as input devices
when you install software or copy data to your system. You use tape cartridges as
output devices when you copy software or data from your system. You can copy
individual files or programs, or you can copy (back up) the contents of a fixed
disk. Tapes are commonly used to archive data.
Mass Storage Controllers and Adapters
All mass storage devices require a controller to control activity between the CPU
and the mass storage device. While the controller for a DSSI storage device
is built into the device, other storage options require a controller module in
your system’s card cage. The controller for the TK70 tape drive is the TQK70;
the KDA50 is the controller for RA-series disk drives. Each KDA50 controller
supports up to four RA-series disk drives. Other controllers are KRQ50 for the
RRD40, KLESI for the TU81, and KFQSA for the DSSI.
The KZQSA adapter lets the CPU communicate with the SCSI tape drive or
RRD-series compact disc drive. Each KZQSA adapter can support up to two of
the following drives: TLZ06, TSZ07, RWZ01.
The CPU communicates with DSSI devices through a DSSI adapter. The adapter
allows the CPU to communicate with the devices connected to a DSSI bus. Your
system has a minimum of two CPU-native DSSI adapters providing two separate
DSSI buses. A third and a fourth DSSI bus can be added to the CPU module
by connecting a DSSI daughter board. The daughter board consists of two DSSI
adapters, providing two additional, separate DSSI buses.
1–22 System Overview
