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Chapter 5. Managing Storage

There were also proprietary interfaces from the larger computer vendors of the day (IBM and DEC,

primarily). The intent behind the creation of these interfaces was to attempt to protect the extremely

lucrative peripherals business for their computers. However, due to their proprietary nature, the de 

vices compatible with these interfaces were more expensive than equivalent non proprietary devices.

Because of this, these interfaces failed to achieve any long term popularity.

While proprietary interfaces have largely disappeared, and the interfaces described at the start of this

section no longer have much (if any) market share, it is important to know about these no longer used

interfaces, as they prove one point   nothing in the computer industry remains constant for long.

Therefore, always be on the lookout for new interface technologies; one day you might find that one

of them may prove to be a better match for your needs than the more traditional offerings you current

use.

5.3.2. Present Day Industry Standard Interfaces

Unlike the proprietary interfaces mentioned in the previous section, some interfaces were more widely

adopted, and turned into industry standards. Two interfaces in particular have made this transition and

are at the heart of today's storage industry:

SCSI

IDE

5.3.2.1. IDE/ATA

IDE stands for Integrated Drive Electronics. This interface originated in the late 80s, and uses a 40 pin

connector.

Note

Actually, the proper name for this interface is the "AT Attachment" interface (or ATA), but use of the

term "IDE" (which actually refers to an ATA compatible mass storage device) is still used to some

extent. The remainder of this section uses the interface's proper name   ATA.

ATA implements a bus topology, with each bus supporting two mass storage devices. These two

devices are known as the master and the slave. These terms are misleading, as it implies some sort of

relationship between the devices; that is not the case. The selection of which device is the master and

which is the slave is normally selected through the use of jumper blocks on each device.

Note

A more recent innovation is the introduction of cable select capabilities to ATA. This innovation re 

quires the use of a special cable, an ATA controller, and mass storage devices that support cable

select (normally through a "cable select" jumper setting). When properly configured, cable select

eliminates the need to change jumpers when moving devices; instead, the device's position on the

ATA cable denotes whether it is master or slave.

A variation of this interface illustrates the unique ways in which technologies can be mixed and

also introduces our next industry standard interface. ATAPI is a variation of the ATA interface and

stands for AT Attachment Packet Interface. Used primarily by CD ROM drives, ATAPI adheres to the