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Hard Drive
Top performance of a hard drive is not so critical. Many high-quality hard drives made today are fairly close to each other in terms of overall speed and noise. I've used many Western Digital and IBM/Hitachi Deskstar hard drives, but I'd also be quite satisfied with a Seagate hard drive. Storage space has gotten less expensive so hard drives with capacities of 250GB and higher make sense.
I like using one hard drive for non-RAID systems. It reduces the heat burden on the PC, and it's always possible to upgrade to a faster, bigger hard drive when the time is right.
For most computer components, I don't like to use "white boxes" (OEM versions) since they are not as complete as the retail box. The hard drive is one exception. The retail box does not include much more other than the hard drive itself. The retail box may include mounting brackets, which many computer cases don't need including the one I'm using, and mounting screws, which you can get in ample quantity at Radio Shack or Home Depot. The retail box also includes disk utilities, but these can be downloaded from the manufacturer using the links I have below.
The hard drive must be of high quality. While this statement is true for all computer components, a failed hard drive may very well mean the loss of all your data. Nearly anyone who has dealt with numerous hard drives over the years can relate at least one personal horror story about a hard drive. It may be a story that is merely deeply disturbing such as the hard drive being recalled, or a catastrophe such as a complete hard drive failure. It's therefore not difficult to come across someone who understandably states they will "never buy that brand hard drive again". While the hard drive brands I discuss on this page are the most well-regarded in the industry, no hard drive maker has a completely unblemished reputation.
The hard drive interface primarily in use today is the newer serial (SATA) interface. The older IDE parallel ATA (PATA) interface is not well supported on many motherboards today. A motherboard may come with support for both interfaces. However, if a motherboard supports only one IDE interface then this is done with optical drives in mind. A hard drive and optical drive should not share the same IDE interface since the hard drive will run at the much slower speed of the optical drive. In this situation, PATA hard drives should be accommodated with an add-on IDE card.
I'm using the Western Digital RE4 1000GB SATA II hard drive. These images show how the SATA hard drive looks when viewed from the front and back, and a readable close-up of the label on the SATA hard drive. PATA hard drives look nearly identical, with the only difference being in some of the connectors on the back. Click on any picture to see it enlarged. Today, both SATA hard drives and PATA hard drives are commonly in use. SATA hard drives are theoretically faster than PATA hard drives since SATA hard drives have a maximum bandwidth of 150 MB/s (megabytes per second) and PATA hard drives have a maximum bandwidth of 133 MB/s (ATA133). But a home computer has difficulty utilizing the full bandwidth of a hard drive under any circumstance with the exception of benchmark tests. Many highly regarding PATA hard drives support a maximum bandwidth of 100 MB/s (ATA100) since the computer can't fully utilize even that bandwidth. My own unscientific tests confirmed this when I tested both a SATA and PATA Western Digital Caviar SE hard drive. While the SATA hard drive achieved better total bandwidth on the benchmarks, the ATA100 PATA hard drive actually did a little better in real-world situations. The SATA hard drive took 18 seconds to boot Windows XP and 77 seconds to copy 40 files totaling 1.28GB (gigabytes). The PATA hard drive took 17 seconds to boot Windows XP and 71 seconds to copy the same file set. The bandwidth of the interface does not dictate which hard drive is faster. To summarize, the faster hard drive is not the one with the faster interface. The faster hard drive is the hard drive that has the larger buffer size and that performs better mechanically to improve performance in areas such as latency and seek times.
Even so, SATA hard drives are replacing PATA hard drives since SATA hard drives can continue to improve. In fact, motherboards and SATA hard drives have already mostly evolved to support SATA II with a maximum bandwidth of 300 MBps. While a PATA hard drive cannot be made with a transfer rate greater than 133 MB/s, SATA hard drives are planned to reach 600 MB/s by the end of 2007. Some day the rest of the computer will be efficient enough to put that extra bandwidth to use. Many motherboards provide support for both SATA and PATA hard drives, even to the extent that both types of hard drives can be used in the computer at the same time. This is quite handy since it is not uncommon for computer builders to want to include a PATA hard drive from their old computer in the new one.
While the extra bandwidth is of no real benefit in today's computers, there are other practical advantages that are nice, if not compelling. First, SATA uses smaller cables to connect the hard drive to the motherboard than the bulkier ribbon cables used by IDE hard drives. This is significant because the IDE ribbon cables are big enough to easily block air flow inside the computer case and lessen the effectiveness of case fans. But as long as you take care to run the IDE ribbon cables out of the airflow then SATA provides no real advantage. Second, a SATA cable can be as long as 39.4 inches, whereas IDE cables should not exceed 18 inches. But it's rare to need a cable longer than 18 inches to connect the motherboard to the hard drive. Third, a SATA cable has less chance of electrical interference occurring on the connection between the hard drive and motherboard since it is serial, whereas IDE is parallel with 40 wires running along the connection. That makes sense, but IDE computers seemed to do just fine in practice.
The description of a SATA hard drive can get confusing since it may be identified as SATA I or SATA II, or it may be described as SATA when it is really SATA II. Or it may described as a SATA 150 hard drive, or SATA 300 hard drive, where the number indicates the interface bandwidth. The thing to look for is the speed (the interface bandwidth). A SATA hard drive that supports an interface of 150 MB/s is SATA I. A SATA hard drive that supports an interface of 300 MB/s is SATA II. Technically, both are SATA hard drives. The terms SATA I and SATA II are commonly used, but are not official terminology. The standards group that defined the 300 MB/s SATA standard was named SATA II, hence the label given the hard drive, but later changed their name to SATA-IO. The SATA I hard drive interface bandwidth may also be described as 1.5 Gb/s (gigabits per second). Similarly, the SATA II hard drive interface bandwidth may be described as a 3.0 Gb/s. The official Serial ATA International Organization web-site is here.
Using a hard drive with a capacity greater than 137.4GB can be more problematical than smaller drives. Such hard drives require that the newer 48-bit addressing standard be supported by the computer's motherboard chipset drivers, BIOS, and by the operating system. Since it's newer, this support may not come already installed in off-the-shelf products (once again, the "six month rule of delayed acquisition" proves it's worth). As far as the operating system support for 48-bit addressing, Microsoft provides How to enable 48-bit addressing for hard drives in Windows XP and How to enable 48-bit addressing for hard drives in Windows 2000 support articles. Windows XP supports 48-bit addressing beginning with Service Pack 1.
Hard drive choice should also take into consideration noise level and heat generation. The Western Digital Caviar SE models fare very well on these criteria when compared to other top performing drives. I can't even hear the the hard drive in My Super PC at all over the fans - and I use relatively quiet fans!
Other features of hard drives.
NCQ. Native Command Queueing. The purpose of this feature is to improve performance. A hard drive with this feature can reorder read/write commands to do them in the most efficient order. Sounds interesting, but practically speaking it makes no improvement.
TLER. Time Limited Error Recovery. The purpose of this feature is to improve the reliability of a hard drive in a RAID configuration. A regular hard drive, one without TLER, works under the assumption that it is on its own in the world and does everything possible for as long as it deems appropriate to secure the data. It cannot tell the RAID controller in the computer anything because it works under the premise that it's on its own. A TLER equipped hard drive can tell the RAID controller to "hold on a sec, I'm still trying", so that the RAID controller does not take it out of service until the hard drive has given up. Someone truly serious about building a RAID equipped computer should probably use hard drives with TLER. Hard drives with TLER (enabled) must be used in a RAID configuration. Hard drives without TLER can still be used in a RAID configuration, but don't have the communication advantage that the TLER hard drive has. In practice, this does not seem to bother many PC builders. Western Digital sells TLER hard drives with a "YS" in the model number, such as WD5000YS. The non-TLER counterpart is the WD5000KS. Western Digital TLER hard drives come with TLER enabled by default, and there's some disagreement about how easy it is to disable it, or even if it's possible.
RAFF. Rotary Acceleration Feed Foward. The purpose of this feature is to improve hard drive reliability by detecting and compensating for vibration. It's intended for use in a RAID configuration, where multiple drives are often packed tightly together. It may be a useful feature to have in rigorous environments, such as a large server, but not so much for home use, although it's likely to be found in a hard drive supporting TLER or very fast rotational speeds.
It's common practice to purchase the hard drive in the "white box" packaging since it's cheaper and since the main thing missing that you would want, namely utilities, are available as free downloads from the manufacturer as described in this table. Although I'm using a Western Digital Caviar SE hard drive, the other manufacturers I list have good reputations.
Manufacturer Utility Comments IBM/Hitachi Drive Fitness Test There are other utilities that may be of interest on the downloads page. Western Digital Data Lifeguard Data Lifeguard is a suite of utilities that includes DLG Diagnostic which performs similar functions to the IBM/Hitachi Drive Fitness Test. Maxtor Powermax The version available at this writing, version 4.06 dated June 2, 2003, states it does not work in computers that use NVIDIA chipset motherboards, meaning it doesn't work with the nForce2 chipset used on the EPoX 8RDA+ and other popular motherboards. Sheesh. They say they're working on a updated version that will support NVIDIA chipsets. Gee, good idea. Seagate DiscWizard Program Suite The version named DiscWizard Starter Edition is the right one for building a new computer. The page also includes other helpful downloads, such as the specifications and jumper settings for all Seagate drives.
Packaging
When the hard drive is purchased in the retail box, it looks something like this.
Click on either picture to see it enlarged. 
Here are the typical contents of the retail box. A utilities CD, mounting screws, a SATA cable, an installation guide, and the hard drive itself sealed in an anti-static bag.
However, the hard drive is frequently purchased as an OEM product ("white box"). When purchased this way, it comes by itself sealed inside an anti-static bag like this example. This is sufficient, since the utilities are available as a download, the mounting screws are common screws found in any good hardware store, the necessary cables come in the retail box of the motherboard, and the installation guide is not really needed.
RAID Hard Drive
RAID is a way of configuring multiple hard drives to improve hard drive performance, hard drive reliability or both. RAID is an acronym for Redundant Array Of Inexpensive/Independant Disks/Drives.
There are many way that a computer can be setup with RAID. The way I've done it is the way most common with computer enthusiasts, which is RAID 0 on the hard drives used to start up the computer. Once the computer is set up, it operates transparently treating the two hard drives as one. At the operating system level, there appears to be one hard drive as usual with whatever partitions are defined. Applications install the same as they do for a non-RAID setup and logical hard drive partitions are created and accessed just the same. Functionally to the computer user there appears to be no difference, except that the total available capacity is the total of the two hard drives and hard drive performance is significantly better.
Note that it's not necessary to use identical hard drives for RAID, but it's a good idea. For example, performance can be contrained if one hard drive runs slower. And storage capacity can be wasted if one hard drive is larger than another - the extra storage in a larger hard drive will not be used.
Here is a brief overview of the possible RAID configurations.
RAID 0 is known as disk striping. It treats two hard drives as one, accessing them in parallel, with the data split across the two hard drives. It provides an appreciable increase in performance, but does not help with protecting data. In fact, it's fair to say that the data is less protected because if either hard drive fails then the data is compromised. Those who use their computer primarily for entertainment prefer RAID 0. Running the same disk intensive operations I mentioned above, my two SATA hard drives configured in RAID 0 took 17 seconds to boot Windows XP and 41 seconds to copy the same file set of 40 files totaling 1.28GB (gigabytes).
RAID 1 is known as mirroring. All data is written to both hard drives simultaneously. The data can be read from either hard drive. It does nothing to help or hurt performance, but provides fully redundant hard drive data. RAID 1 is the other more commonly used form of RAID. It can be practical for those who keep business data or other important data on their computer.
RAID 0+1 combines the capabilities of RAID 0 and RAID 1. There are two groups of hard drives. Inside each group, the hard drives are configured as RAID 0 to get the performance benefit. The two groups are configured to each other as RAID 1, to get the mirroring benefit of data redundancy. A RAID 0+1 configuration requires at least 4 hard drives, two in each group. While this makes RAID 0+1 more expensive than other RAID configurations, RAID 0+1 nevertheless has a strong appeal since it gives the best of both worlds in terms of performance and data protection. And hard drives aren't that pricey, anymore.
RAID 2 is disk striping with multiple hard drives where a small number of hard drives are set aside as a "check disk".
RAID 3 is disk striping over several hard drives with a dedicated hard drive used for parity checking. It provides fast data transfer with a low-cost for data security, but if the hard drive used for parity checking fails then all data integrity is lost.
RAID 4 is similar to RAID 3 with a different means used on the dedicated hard drive to verify the integrity of the data.
RAID 5 is disk striping over multiple hard drives with the parity checking also done over multiple hard drives.
RAID 0 and RAID 1 are the most commonly used. There are even more forms of RAID than what I've listed, including software RAID supported by the Windows operating system. It can be done with a mix of hard drive types, such as two SATA hard drives, two PATA hard drives, or one of each. And hardware RAID like I describe can be setup on hard drives other than the boot hard drives.
My complete recommendations for building a computer with quality components at unbeatable prices is on my home page at Build A Computer Like My Super PC - Cost To Build A Computer. Here again are the recommendations for a hard drive!
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