Using IBM LTO Ultrium with Open Systems - RS/6000 Home

A p p l i c a t i o n
P r o g r a m
( s o f t w a r e )
L T O d e v i c e
d r i v e r
( s o f t w a r e )
H B A d e v i c e
d r i v e r
( s o f t w a r e )
H B A d e v i c e
a d a p t e r
( h a r d w a r e )
L T O t a p e
d e v i c e
What are device drivers?
A device driver is a program that controls a device. Every device, whether it be a
printer, disk drive, or keyboard, must have a driver program. Many drivers, such
as the keyboard driver, come with the operating system. For other devices, you
may need to load a new driver either from the operating system CD or provided
by the manufacturer when you first install the device on your computer.
A driver acts like a translator between the device and programs that use the
device. Each device has its own set of specialized commands that only its driver
knows. In contrast, most programs access devices by using generic commands,
that is, Read, Write, Put, Get. The driver, therefore, accepts generic commands
from a program and then translates them into specialized commands for the
device.
Figure 1-12 is an example of the data flow between an application program and a
LTO tape device. Note the different pieces of code or microcode involved.
Note that the HBA device driver is not always a separate piece of software;
sometimes it’s part of the standard operating system. This is true for some SCSI
adapters — you should check the documentation provided with the card to see if
this applies. For Fibre Channel HBA’s, extra software will almost always need to
be installed.
Figure 1-12 Device data flow
Data flow
The simplified list below reflects the components involved in the data path for
moving data at a file level between disk storage devices and tape.
Problem or performance analysis must be approached by determining which
component of the data path impacts performance.
► Disk device
► SCSI device adapter
► Adapter device driver
► Disk device driver
► Logical Volume Manager
► File system
► Application program
► Atape device driver - tape driver
► HBA adapter device driver
► HBA (SCSI or FC-AL) device adapter
Chapter 1. Introduction to LTO Ultrium with UNIX 25