Are Disks and Files Systems a Feature?

From the user's point of view, there is no reason for disks to exist. From the hardware engineer's point of view, there are three:

  • Disks are cheaper than solid-state memory.

  • Once written to, disks don't forget when the power is off.

  • Disks provide a physical means of moving information from one computer to another.

Reasons two and three are certainly useful, but they are also not the exclusive domains of disks. Other technologies work as well or better. There are varieties of RAM that don't forget their data when the power is turned off. Some types of solid-state memory can retain data with little or no power. Networks and phone lines can be used to physically transport data to other sites, often more easily than with removable disks.

Reason number one—cost—is the real reason why disks exist. Non-volatile solid-state memory is a lot more expensive than disk drives. Reliable, high-bandwidth networks haven't been around as long as removable disks, and they are more expensive.

Disk drives have many drawbacks compared to RAM. Disk drives are much slower than solid-state memory. They are much less reliable, too, because they depend on moving parts. They generally consume more power and take up more space, too. But the biggest problem with disks is that the computer, the actual CPU, can't directly read or write to them! Its helpers must first bring data into solid-state memory before the CPU can work with it. When the CPU is done, its helpers must once again move the data back out to the disk. This means that processing that involves disks is necessarily orders of magnitude slower and more complex than working in plain RAM.

DESIGN TIP 

Disks are a hack, not a design feature.

The time and complexity penalty for using disks is so severe that nothing short of enormous cost-differential could compel us to rely on them. Disks do not make computers better, more powerful, faster, or easier to use. Instead, they make computers weaker, slower, and more complex. They are a compromise, a dilution of the solid-state architecture of digital computers. If computer designers could have economically used RAM instead of disks they would have done so without hesitation—and in fact they do, in the newest breeds of handheld communicators and PDAs that make use of Compact Flash and similar solid-state memory technologies.

Wherever disk technology has left its mark on the design of our software, it has done so for implementation purposes only, and not in the service of users or any goal-directed design rationale.




About Face 2.0(c) The Essentials of Interaction Design
About Face 2.0(c) The Essentials of Interaction Design
ISBN: N/A
EAN: N/A
Year: 2006
Pages: 263

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