Choosing internal mass storage means that you must decide to focus on the best performance, the highest capacity, or both. Western Digital's latest Raptor 150 GB drives lead the Serial ATA race, but the much slower Seagate Barracuda 750 GB leads in capacity. Midsized drives of around 300 GB usually also fall in the middle of the performance curve, and our hard drive charts highlight performance and cost per gigabyte of a broad selection.

A fast drive might not make most programs perform better, but it will certainly make them load faster, and that includes Windows itself.

How much storage you'll need is a function of your usage patterns; Windows itself rarely exceeds 4 GB without additional programs installed, even after many months of collecting temp files, cookies, and other "temporary" trash. Programs can easily consume five times that much capacity, and some games take up to 4 GB on their own! DVDs consume up to 8.4 GB each, so those who love to archive video will find their capacity needs rising quickly.

Remember that hard drives fill from the outside of the platters inward. Constant disk speed and bit size assure that the outer edge of the platter is fastest, so many users choose to place a small system partition up front to make programs load quickly. After several years of trial and error, I've settled on a 40 GB system partition, but this again is specific to my program configuration.

Knowing the size of larger files being stored (such as 8 MP photos or 8 GB movies) and predicting the number of these that the system will collect over its expected life allows the selection of the minimum acceptable storage partition size. Users with multiple partitions can add the system partition and storage partition requirements to choose a single drive with the capacity needed, or split the files across multiple drives.

Though systems typically use a single large disk, several advanced options are available for those who require added performance or capacity. RAID stands for Redundant Array of Inexpensive Disks, a group of methods that allows data to be spread across several disks concurrently. Most motherboards now support at least RAID modes 0, 1, and 0+1, and the newest support RAID 5.

The possible use of RAID affects the number and capacity of drives selected, so a very brief description of these modes is in order:

Level 0 (striping) divides data into chunks that are spread across two (or more) drives at the same time, providing up to double the transfer rate and the combined capacity of both drives. The major drawback is that if either drive fails, the data from both is lost. Level 1 mirrors two (or more) drives so that if one fails, data can be recovered from the other. The major drawback here is that because both drives store the same data, the available capacity is half of the total capacity of the drives. RAID 0+1 allows four (or more) drives to be set up as a mirrored set of striped drives. If one striped set fails, data can be retrieved from the other, but total capacity is still limited to that of one striped set. RAID 5 creates parity bits for data recovery. Data and parity bits are distributed across all drives, increasing transfer rate, while sacrificing only the amount of space required to store the added parity bits (the capacity of one drive in the set).

Generating parity bits for RAID 5 requires processing, which means that RAID 5 via "software" controllers - as found in chipsets - is often a significant resource hog. Conversely, RAID Levels 0 and 1 generate little CPU overhead. Gamers with little regard for long-term data storage may choose Level 0 for performance, and anyone with a significant amount of valuable data may choose Level 1.

Tom's Hardware Guide has reviewed many storage controllers, with several of these articles going into additional detail concerning RAID modes, benefits and consequences.