Computer Hard Drives

Selecting a Hard Drive

The hard disk drive, or simply, the hard drive, is the main storage unit of your computer. It holds all the programs you have installed on the computer along with the operating system. There are several types of hard drives in use today, but you'll probably only consider two different types for building your own computer. The two most common types of drives that are used in PCs today are PATA and SATA type drives. The other type that you might consider is a SCSI type drive. However, due to the cost of SCSI type drives, I'd steer away from them. In many cases, SATA II type drives offer larger capacities along with faster data transfer speeds than SCSI drives.

PATA/IDE

PATA (Parallel ATA) or IDE (Integrated Drive Interface) hard drives have been around for over a decade. Until recently, PATA/IDE drives were the standard for most home and business PC's. They provided excellent performance and lower costs than other available types. PATA/IDE type hard drives are being phased out in favor of SATA type hard drives. The IDE interface is still being used for many multimedia drives, however, even these types of drives are being phased out in favor of SATA types.

SATA

SATA (Serial ATA) drives come in two flavors: SATA and SATA II. SATA drives provide up to 150Mbps/second (1.5GB/second) data transfer rates, and SATA II provides up to 300Mbps/sec (3GB/second) data transfer rates. That figure is destined to be doubled to 6GB/second within the next year. One advantage to SATA is the ability to remove and replace a hard drive (if the motherboard or controller supports it, which most do) without powering the system down.

RAID

RAID (Redundant Array of Independent Disks) is a way of writing data to multiple hard drives to help insure data redundancy or increase drive performance, or both. There are various levels of RAID available depending on how many drives you have installed, and what level your motherboard or drive controller supports. RAID 0, 1, and 5 are the most common levels, and probably the only kind to be concerned with when you build your own computer.

RAID 0 - Striped Disk Array
RAID 0 provides data striping (writing blocks of each file across multiple drives) but it provides no redundancy. RAID 0 is used primarily to improve drive performance. RAID 0 requires a minimum of two drives.
RAID 1 - Disk Mirroring
Disk mirroring is a method of writing data to two disks at the same time. Writing does not degrade performance in any way, but permance is better reading from the disks because data is retreived in alternating blocks from each disk, thus cutting read time approximately in half. RAID 1 does provide data redundancy since both disks hold duplicate data. RAID 1 requires two drives.
RAID 5 - Block Interlieved Distributed Parity
For a home, and most business computers, RAID 5 provides the best performance and data protection. It does this by data striping at the byte level along with storing parity error correction data. If a drive fails, the striping and parity correction allows data on the failed drive to be restored. RAID 5 requires a minimum of three drives.