Technologies:

A PC Guide That Won’t, Technically, make your Head Explode.

by Rob Cheng and Bill Zahren

Hard Drive
(The Electronic House 'o Data)

While on their quest for faster, more powerful and easier-to-use PCs, computer crazies have managed to find time to turn hard drives into super bulbous data caverns.

The "HDD" above the little light on the front of your computer stands for Hard Disk Drive, which almost everyone on earth who doesn't own a pocket protector simply calls the "hard drive."

When the HDD light flickers and you hear those little clicking noises, that means the hard drive is working. Try to notice some time how often that little HDD light pulses to life. The hard drive spins like a yarn maker with a big backlog - constantly.

The hard drive stores data. That's its entire mission in electronic life. Bring it in, store it, send it out. If only the rest of life were that simple.

Your hard drive is about the size of two or three CD cases stacked on top of each other. If you could look inside the hard drive, and we don't recommend it, you would see from one or more little disks called "platters." The platters are 3.5 inches in diameter in a desktop hard drive, 2.5 inches wide in a portable. An arm extends over each platter and contains tiny heads that transfer data to and from the disks.

The hard drive's platters rotate at up to 5400 rpm. That works out to 90 revolutions per second. The technical term for that kind of speed - "cranking, big time."

Hard drive makers worry about three main things: how much data they can mash onto one platter (called "areal density"), how fast the hard drive can find the data (access time), and how fast the data flows from the hard disk to the RAM or Central Processing Unit (throughput).

The company that masters all three areas experiences a period of market smugness during which they make lots of cash. The smugness usually doesn't last, however, because technology in all these areas constantly changes due to savage competition and market demand for higher and higher performance. This results in a hard drive melee featuring companies trying to outdo each other, which pretty much defines the computer industry as a whole, come to think of it.

Areal density (the amount of data you can pack onto each platter) is important because it makes more efficient use of the space on your hard drive's platters. So the per-platter figure determines the maximum capacity of one hard drive.

The accounting department gets all dry mouthed when they consider the second areal density fact of life: The number of platters, not the amount of space on each, generally determines the cost of making the hard drive.

So a hard drive with three 100MB platters (300MB total) costs the same to make as one with three 500MB platters (1.5GB total). Tough for the 300MB drive to compete with a 1.5GB drive when they cost about the same.

Improvements in areal density so far have made the 3.1GB storage monster the biggest hard drive commercially available today.

Just 18 months ago, computer people hailed ownership of a 1GB hard drive as a huge feat of electronic prowess. It appeared cavernous. Your word processor files seemed like little BBs in a box car. Your fellow nerds and geeks at the local computing club revered you as a god for your 1 gig wonder.

Today, an 850MB, which seemed like the Sprawling Data Mansion of the Apocalypse when you bought it, seems like Ye Little Old Data Tool Shed compared to the 3GB Mondo Jumbo Storage Pit. What makes your storage needs grow faster than a well-fed 6 year old? The lure of a forest of cool digital stuff that gets thicker by the second. And if it's digital, a hard drive can store it.

Faced with all that digital candy, we naturally want everything. Pictures, video, audio, games, data bases, the national telephone book, every word of a Congressional debate on yam production. People want to keep stuff. The urges combine to make your hard drive a lot like the closets in your house - no matter how huge they are, some day you will fill them. It's just some kind of law of nature or something. Maybe it's connected to the tides or astrology. We don't know. But, no matter what size hard drive you get, it will one day be full. We promise.

And that will be a very, very dark day. A day that will visit you again and again in your nightmares. Because the "disk full" message will likely come while you're working on something so important you'd consider losing a finger in order to keep the file.

Faced with the prospect of having a power surge scatter their complex spreadsheets to the wind, many people dive into their file manager and start killing everything in sight so they have space to save it. Indiscriminate electronic murder. Megabyte carnage. Everything must go until you make room for the file.

What's been filling those ever larger electronic closets? Multimedia files and "other data types." Multimedia files today grow faster than corn in South Dakota. As hard drives have gotten bigger and processors more muscular, multimedia software programmers have expanded their software to be bigger, stronger, more graphic and more complex than ever. Some games easily blast over 60MB by themselves, no problem.

And how many people put a CD-based game on their hard drive and then, when done playing, go in and kill it off so they can load it again next time? Nobody we know.

So you load on Space Hog Game number one today, throw Mr. Huge Entertainment Pack on next week and add Megabyte Titan productivity application after that, and pretty soon your electronic closet runneth over. Yeah, verily, we say unto you: bummer.

"Other Data Types" refers to stuff like video clips, audio files, things you grabbed off the World Wide Web, all the things being converted from analog to digital, allowing them to be stored in a hard drive.

Because the world is turning digital, your PC can now literally become a photo album, video library, newspaper, magazine and book archive - a repository of reams of documents, cases of videos and hours of sound. For example, Rob has stored on his Gateway(tm) Liberty(tm) portable PC about a billion e-mails going back three years or more, a few years worth of select magazines, audio of things like Michael Jordan talking about why the Bulls smash everyone in sight, random hunks of the World Wide Web, ideas for a million things and trillions of characters of text. He takes the thing everywhere. It's kind of scary.

After you get by the size question, hard drive performance centers on access time and throughput. Access time measures how fast the hard drive can find a specific file within the digital sea. Throughput indicates how fast it can put that data through to the DRAM (Dynamic Random Access Memory) or processor. When working with big files, quick access time (measured in milliseconds) isn't as important as throughput (measured in megabytes per second). Some companies offer hyper-huge hard drives with blazing access times but completely snail-like throughput. That means it takes the drive no time to find your huge word processor file but forever to get data from it. Ideally access time will be a very low number and throughput will be a very high number.

But how do they do it? How can hard drives find a bit of data equivalent to the size of a playing card inside a 100-yard warehouse?

Think FAT. That's short for "Go On A Diet." Just kidding. It's short for "File Allocation Table." Think about how you would look up information in a big book. Go to the index, unless you're one of those people who flips pages, severely annoying the rest of us.

The FAT is basically the hard drive's index. Hard drives are twice as organizationally anal than anybody you'll ever know. The FAT knows exactly where every bit of data is located inside the House o' Data. So, when you open a file, the FAT locates it and the mechanical parts of the hard drive fetch it.

Here's the tricky part: When you delete a file, it's really still there. It's still in the Data Barn. We swear. You've just deleted its name off the File Allocation Table so the hard drive sends you the fun "file not found" message. The actual file will still be on the hard drive until the next time you save something new. Then the file really gets deleted because the new file writes over the old.

If you really want to delete data for real, you need to either kill it off the FAT and then defragment the hard drive or reformat the hard drive entirely. Ouch. Please don't do that. Reformating deletes absolutely EVERTHING on the hard drive. Period. Usually not a good thing.

Defragging basically reorganizes the data barn to make it more efficient. When you kill a file and then defrag, the hard drive will write over the old file with another existing file while it's reorganzing the hard drive. That makes the old file gone forever.

To help hard drive performance rock and roll even more, makers build in a dab of RAM called "cache." The hard drive will load frequently needed data into the cache where it can go to and from the processor faster. An algorithm (you don't want to know the definition, trust us) controls what gets loaded into the cache. Direct Memory Access, or DMA (acronyms, we can't get enough of them!) also enhances hard drive performance. DMA lets the hard drive get data to and from RAM in a burst, without getting the CPU involved. The CPU normally has to tell the hard drive when to send stuff to the RAM. But the CPU has a ton of things going on, and frankly, it would like the hard drive to take some initiative and just shoot data directly to the RAM, darn it. The CPU shouldn't have to tell you to do everything, Mr. Hard Drive. If the CPU doesn't have to say, "OK, hard drive, send these five files to the RAM, and be quick about it.," The hard drive just instead blasts the data over without the great CPU command, the data gets there quicker and everyone remains far less surly.

And - go with us on this one - a surly power computer user is a very, very bad thing.

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