Hard Drive Capacity

Hard drive capacity measures the amount of storage space available to you for saving files. An average home computer will work well with a 40GB (gigabyte) hard drive, while a more advanced computer that uses heavy duty software applications with large files may require much more storage space - 200GB and up.

Hard Drive Disk Speed

The hard drive disk speed (or "rotational speed") is measured in RPMs (revolutions per minute) and indicates how fast your drive can read and write data. On average, hard drives spin anywhere from 4,200 RPM's to 15,000 RPM's. As the RPM increases, expect the price and performance to increase.

Hard Drive Cache

A hard drive cache is designed to enhance the speed of data retrieval. The cache acts as a buffer and temporarily stores pieces of data that the computer's processor is likely to use next, reducing the computer's "seek" time. As the hard drive cache increases, so does the computer's overall performance. Most hard drives comfortably use a 2MB cache, but 8MB and 16MB options are becoming more popular.

Operating System

Operating system compatibility should also be a deciding factor when choosing your new hard drive. Most drives are pre-formatted for use with a Windows-based computer so if you're a Mac or Linux user you should be aware of possible compatibility issues and you may need additional software to get your operating system to recognize the new hard drive.

Data Transfer Rate

Data transfer rate, sometimes referred to as "throughput", measures how quickly the hard drive can pass digital information to another device. It's usually measured in megabits (million bits, Mbps) or megabytes (million bytes, MBps) per second. The higher the number, the quicker the data gets moved and the less time you have to wait between actions.

Available Options

Internal Hard Drives

Internal hard drives fit into the ìbaysî inside your computer case. Most computers have at least one open or available bay but itís a good idea to double-check before you buy your new internal hard drive. If youíll be installing the hard drive yourself, be sure to purchase an upgrade ìkitî which will provide you with all of the necessary hardware (cables, mounting bracket and rails) and software to safely complete the installation.

Pros: Internal drives often have faster transfer rates and tend to cost less than external hard drives.

Cons: Installation can be complicated.

External Hard Drives

External hard drives offer the same great storage capacity solutions as internal drives and are usually easier to add onto your system because they do not require opening up your computer. They are often ìplug-and-playî, connecting to your computer via USB or FireWire, which means that theyíll be up and running as soon as you plug them in.

Pros: Easy installation. Portability makes them a perfect solution for backing up multiple computers or transferring large amounts of data among many different locations.

Cons: External drives are more susceptible to damage due to accidental bumping or dropping.

Laptop Hard Drives

Laptop hard drives are available as internal or external solutions, similar to desktop hard drives. Youíll be in close contact with your laptop hard drive, so make sure it doesnít produce a lot of heat or noise. Also, shop for a laptop hard drive thatís lightweight and wonít drain your battery power.

Before buying your new laptop hard drive itís a good idea to take a look at your laptop computerís user manual, which will tell you if it was designed with easily swappable hard drive device bays. Some older laptops may be more difficult to service and will require that you have your new hard drive installed professionally.

Pros: Allows you to carry large amounts of data with you as you travel.

Cons: Older laptops may require additional software or a professional installation.

Network Attached Storage (NAS)

ìNetwork attached storageî is a configuration made up of a stand-alone hard drive connected to a network for sharing and storing files. This setup allows each computer on the network to access the data on the NAS. In most cases you can plug these hard drive storage devices right into your router and instantly begin sharing your files across the network.

Pros: Inexpensive storage solution providing backup space for multiple computers.

Cons: Slow file transfer speeds.

What will you be using your new hard drive for?

We've broken down hard drive users into three categories to show you which type of hard drive will work best for each one. As you're shopping, remember it's always a good idea to buy a little more storage space than you think you need to give yourself plenty of room to grow.

Multimedia or Video Editor

If you'll be working with large multimedia files, the speed and size of your hard drive is essential. You'll need a drive that can handle a heavy workload while providing reliable space for archiving your projects. Choose an internal hard drive, if possible, as they have the fastest communication with your processor.

Hard Drive Capacity: 300 GB

Enclosure Type: Internal

Data Transfer Rate: 320 MBps (Megabytes per second)

Rotational speed: 10000 RPM

Level 2 Cache: 8 MB

Price: $170 to $330

Graphic Artist or Photographer

Working with resource-intensive applications can really slow down your system. To compensate for this, look for a hard drive with a super-fast transfer rate and lots of storage space.

Hard Drive Capacity: 100GB or more

Enclosure Type: Internal

Data Transfer Rate: 240MBps ñ 480MBps

Rotational speed: 7200 Rpm

Level 2 Cache: 8MB

Price: $60 and up (depending on hard drive capacity)

Traveler

Flash drives are a very affordable and convenient solution for the frequent traveler. Small, light, and powerful, flash memory hard drives give you easy access to your files when you're on the road. Most flash memory drives connect to your computer using USB or FireWire and require very little installation or configuration. Because they have no fragile internal moving parts, flash memory drives are very rugged and reliable.

Hard Drive Capacity: 128MB up to 80GB

Enclosure Type: Flash Memory - External

Data Transfer Rate: 30 ñ 40 MBps

Rotational speed: 5400 - 7200 Rpm

Level 2 Cache: 2MB up to 8MB

Price: under $100 to $300

Important Terms

DMA - (Direct Memory Access) allows your computer to transfer data from its memory to another device without passing it through its CPU (central processing unit). DMA is a big time-saver and enables your computer to make quick backups and support real-time applications.

DRAM - (Dynamic Random Access Memory) is a common type of RAM (Random Access Memory) used for personal computer components. RAM temporarily stores large pieces of data for fast direct access. DRAM requires that it refresh itself constantly to hold data in its memory. DRAM is less expensive than SRAM (Sequential Random Access Memory) but tends to be slower due to its constant refresh cycles. A computer's main RAM is usually on a dynamic RAM (DRAM) chip.

IDE - (Integrated Drive Electronics) is a standard interface for connecting your computer to its storage drives. It's based on parallel technology, which processes bits of data simultaneously.

EIDE - (Enhanced Integrated Drive Electronics) is an enhanced version of IDE that makes it possible to access a hard disk larger than 528 Mb. EIDE also provides faster access to the hard drive, support for Direct Memory Access (DMA) and support for additional drives like CD-ROM and tape drives.

Flash Memory - A fast type of computer memory that retains data even when the power is turned off. It is often used for digital cameras and music players.

Level 2 Cache - Cache memory is random access memory (RAM) that a computer's microprocessor accesses more quickly than it can access regular RAM. As the microprocessor processes data, it quickly looks first in the cache memory. If it finds the data it needs there it doesn't have to do the more time-consuming search for data from larger memory. Cache memory is often described by how close it is to the microprocessor, for instance, an L1 (level one) cache is on the same chip as the microprocessor and an L2 (level two) cache is usually on a separate static RAM (SRAM) chip.

SATA - (Serial Advanced Technology Attachment) is a new interface for connecting your computer to its storage drives. It's based on serial technology, which processes bits of data sequentially.

SCSI - (Small Computer System Interface) is a set of ANSI (American National Standards Institute) standard interfaces that allow your computer to connect to peripheral components - such as disk drives, tape drives, CD-ROM drives, printers, and scanners - faster and more flexibly than previous interfaces.