How to build your own personal computer - Kitchen Table Computers
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Choosing a Hard Drive

 

What, Exactly, is a Hard Drive?

The hard drive is the component on your computer that stores data semi-permanently (that is, until you or a program tell the computer to delete that data).

Unlike RAM, the hard drive is a semi-permanent storage device. It is non-volatile, in geek terms. That means it continues to hold data even when the power to the drive is turned off (or even if the drive is removed from the computer, for that matter).

RAM, on the other hand, is volatile, which means that once the power is removed from the RAM, the data that was on the RAM disappears.

A properly functioning hard drive will retain data until the user or a program instructs it to delete or modify that data. This is why it's important to securely erase the data on a hard drive before discarding it. In fact, a cottage industry exists that specializes in destroying the data on hard drives so they can be disposed of.

 

Types of Hard Drives

Conventional Hard Drives

Cutaway view of hard driveA conventional hard drive (sometimes called a "disk-type" hard drive) is a stack of magnetic disks that spin at very high rates of speed (7200 RPM for a modern EIDE or SATA drive, and 10,000 RPM for a SCSI drive) and are used to store your computer's data.

The disks are enclosed in a protective casing that also contains the drive motor, servos, actuator arms, read/write heads, and the logic circuitry necessary to interface with the system and read from and write to the magnetic disks. Hard drives also contain their own ROM, RAM cache, and controller circuitry.

Conventional hard drives have some disadvantages. They are sensitive to physical shock, vibration, magnetic fields, and orientation (in general, they should be mounted either horizontally or vertically -- not anywhere in between). Because of the gyroscopic effect of the spinning disks, moving them while they are spinning is a very bad idea. They also consume a lot of power and generate a lot of heat.

 

Solid-State (SSD) Hard Drives

Best Buy Co, Inc.

A newer type of hard drive that's becoming very popular is called an SSD hard drive. SSD stands for "solid-state drive," or sometimes (and incorrectly) "solid-state disk." The latter term is incorrect because SSD drives have no disks, heads, actuators, or other moving parts. They store data on microchips utilizing NAND-based flash memory, which is the same technology used for USB drives and memory cards for cameras and other devices.

SSD drives have many advantages over conventional drives. SSD drives are less sensitive to vibration, make no noise, consume less power, generate less heat, never need defragmentation (in fact, it's recommended against), need no time to "spin up," and may be mounted in any orientation.

At the higher end of the price range, SSD drives are also must faster than conventional drives, providing consistently fast data access and virtually no latency. But watch out for cheap, low-end SSDs from no-name manufacturers. They may actually be slower than conventional disk drives, as well as unreliable. If the price seems too low to seem true, then there's probably a reason. Search on the company's reputation and the drive model before buying.

All those advantages don't come for free, however. SSD drives are still much more expensive per gigabyte than conventional hard drives Although prices are starting to come down).

SSD drives use the same interface technology as conventional drives, so a conventional drive can be directly replaced by an SSD drive.

There's also something called a "hybrid drive" or "SSD-HDD" drive that utilizes SSD technology for the drive's cache, but disks for storage. The idea is that frequently-accessed data is offloaded from the slower disks to the faster SSD cache, and then pulled from cache as needed by the system, which improves performance at a lower cost than that of a full-SSD drive.

 

Types of Hard Drive Interfaces

The interface is the way that the hard drive is connected to the rest of the computer. There are several different types of hard drive interfaces used for desktop computers.

  • Very high-end computers often use SCSI (pronounced "skuzzy" and standing for "Small Computer Simplified Interface") drives, which are capable of high data transfer rates. But for most home computer users, SCSI drives are prohibitively expensive. They also require special controllers and are a bit complicated for most beginners to configure. As SATA-interfaced SSD drives get faster and faster, the market for SCSI is beginning to shrink even for high-end computers.

  • Until recently, most home and small office computers used EIDE (Enhanced Integrated Drive Electronics) drives, which were commonly known as ATA (short for ATAPI) drives. Nowadays they're called PATA (Parallel ATA) drives, to distinguish them from SATA (Serial ATA) drives. The designation ATA is followed by a number (33, 66, 100, or 133) that gives the drive's maximum data transfer rate in MB/second. ATA-33 and ATA-66 hard drives are now obsolete. ATA-100 and ATA-133 are still available, but are rapidly being replaced by SATA drives.

  • Almost all new desktop and laptop computers use Serial ATA (SATA) drives. SATA replaced the EIDE hardware interface while maintaining the ATA command set, enabling much faster data transfer rates than EIDE drives, but with fewer compatibility and configuration issues than SCSI drives. SATA drives also are less expensive than SCSI drives of comparable capacity.

 

How Big a Hard Drive do I Need?

Well, that depends.

Hard drives with capacities well in excess of a Terabyte are now available. But a 500 GB drive is probably plenty for a single user who mainly uses standard office applications and doesn't store a lot of graphic, video, or music files. Chances are that the drive will wear out before you fill it up.

But 500 GB drives are considered pretty small as hard drives come these days, so you'll probably find that you can buy a much larger drive for about the same price.

If you're into digital photography, music, or video, then you'll want a much bigger drive for your homebuilt computer -- probably something in the 1 TBto 2 TB range. The same holds true for a computer that will be used by multiple users.

It's a lot easier and more economical to install a larger drive to begin with, then to have to install a larger drive later on when you have run out of drive space. So when pondering whether it's worth an extra ten bucks to step up to that bigger drive, the answer is probably yes.

There are many companies that make hard drives, but I happen to like Seagate, Samsung, and Western Digital.

 

Understanding the Importance of Hard Drive Cache

Hard drive cache chipThe hard drive cache (or buffer) is a little bit of DRAM on the hard drive's logic board that stores frequently-requested data so it doesn't have to be repeatedly read from the drive. This speeds things up a lot, and a larger cache can dramatically improve hard drive performance and computer speed.

The amount of hard drive cache at the time of this writing ranges from 2 MB on el-cheapo drives, to 64 MB on extremely high-end drives. Personally, I suggest you don't use a drive with less than 16 MB cache. Not only does more cache improve the computer's performance, but drives that come with a larger cache tend to be better-built, higher-end drives with longer warranties.

One way to save a little money is to look for a drive with a lot of cache, but which is of a size that the manufacturer is discontinuing. As drives in excess of a Terabyte are now available, many manufacturers are discontinuing production of their smaller drives that are still very high-end in terms of quality. These drives are usually sold at deep discount, but they're still great drives. They're just smaller than what people want these days. But they may be more than big enough for your needs.

So what it boils down to is this: Look around for a high-quality hard drive with a lot of cache, in a size that satisfies your storage needs, but that doesn't break the bank. Don't think you need the biggest drive in the store unless you really, truly, honestly need all of that storage. You'll get better performance from a smaller drive with a larger cache, than from a larger drive with a smaller cache.

 

Saving Money on a Hard Drive

Most hard drive manufacturers make hard drives in both OEM (Original Equipment Manufacturer) and consumer packaging. The consumer versions typically come in brightly-colored boxes that contain the hard drive, a cable (maybe), the screws, an instruction manual, and a bootable utility that helps partition the drive or copy an existing drive to the new drive. The OEM version typically comes in a plastic bubble that contains the drive itself, maybe the screws, and nothing else.

Many home computer builders prefer the OEM drives because they're usually much less expensive than the comparable consumer-packaged drives. But there are a couple of things to be careful of. Firstly, OEM drives are packaged in bulk cases that provide good shipping protection while the whole crate is intact. But once the package is opened and the individual drives removed, they have a lot less protection than a consumer-packaged drive. So the likelihood of an OEM drive being damaged in shipping is slightly higher than a drive that's consumer-packaged. (Reputable vendors know this and add their own cushioning, however.)

Secondly, you probably won't be able to use the warranty on an OEM drive if it should fail. OEM drives are intended for sale to computer manufacturers, and the warranty exchange program works differently for OEMs. Long story short: Unless you're registered with the drive manufacturer as an OEM, the chances are they they will not honor any warranty claim you file on an OEM drive. (The vendor from whom you purchased it may honor the warranty, however. Ask before you buy.)

 

Remanufactured or Reconditioned Drives

Most manufacturers also sell "remanufactured," "reconditioned," or "factory-repaired" drives. Personally, I don't think the price difference justifies the chance you're taking unless the drive carries the same full warranty as the company's new drives. The way I see it, if the drive manufacturer is telling me the drive's "good as new," but doesn't want to warrant it, something isn't right. If you're on a tight budget I'd say go with a new OEM drive rather than a refurbished one.

 

Next Page -> ATA Hard Drive Configuration

Revision date: March 7, 2012


 

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