Hard Drive Buying Guide

Benefits of using a Hard Drive (back to top)

A hard disc drive is a crucial piece of equipment for a personal computer. It houses the core operating system, user files and software applications. Depending on their needs, a user may also have an external drive for the sole purpose of data portability. Such drives may have the ubiquitous USB interface or the up-and-coming Firewire interface, now widely accepted among industry professionals and drive manufacturers. The internal drive comes in a variety of interfaces such as the ever-compatible IDE/ATA interface, the scorcher SCSI interface or the recently developed SATA interface for excessive data transfer speeds.

While storing data is quite important, who stores data where can be quite an intriguing guessing game. For normal operations involving data storage, loading operating systems, playing games, etc. a regular hard disk may easily take on the task. For corporate scenarios such as: implementing a multi-user computing environment, installation of file and print servers, internal and intranet mail systems, data backup for security and redundancy, operational data centers, etc. high end drives with high rotational speeds and high speed data transfer interfaces would fit the bill.

1. How Hard Drives Work (back to top)

A hard drive consists of a set of high density magnetic media, usually the shape of round disks called platters, mounted on a rotating spindle. This rotating spindle is mounted on a special servo motor controlled by an advanced set of electronic circuitry. The servo motor spins at a continuous speed depending on the model of the drive or a specific make of a manufacturer. The speed at which the motor spins is calculated in rotations per minute or RPM. The RPM of a drive suggest the actual speeds at which data can be retrieved or stored to the drive at any given time. The higher the RPM, the faster the actual data transfer rate. The data on the disks is read through a magnetic arm also controlled through another special servo motor. The data read through this arm is transferred by the control circuit via the interface bus to the main CPU bus or main hard disk controller on the motherboard to be processed by the main processor or CPU. All information read from the hard drive or written to the hard drive passes through the very same route. This interface bus can be either the IDE/ATA interface, SCSI bus or the newer SATA standard. Each these interfaces support varying rates of data transfer as well as distinct connectors to connect the hard drive to the motherboard. Importantly, none of the standards are compatible with each other and cannot be interconnected. Though, a drive of each kind can exist in a same PC, it needs separate controllers, either integrated onto the motherboard itself or available as special add-on internal cards in the market, for connecting to the motherboard. The following sections detail the types of drives that are available in the market catering to different needs of people in varying types of circumstances.

2. Types of Hard drives (back to top)

Hard drives are generally classified into two types. The first type includes most of the drives commonly found in the market. These drives reside inside the PC cabinet or inside the small form factor of a laptop. While the mechanisms of both the drives are same, the only differentiation is the form factor. The normal PC hard drive measure 3. 5" in width and usually less than an inch in thickness. The drive rotation speed may vary anywhere between 5,400 RPM to 15,000 RPM. A laptop drive is much smaller measuring around 2. 5" or even 1. 8" inches at times in width and at most 1 cm in thickness. These are much faster than external drives, cheaper, durable, and offer larger storage capacities than external drives.

The second type of drive is an external drive which consists of a simple laptop drive encased in a metallic or plastic casing with special interface ports such as USB or FireWire ports for connecting to a PC for transferring data. These are never connected to the PC motherboard as they are meant to be connected with either of the mentioned ports available for connectivity on the front or rear panel of the PC casing. These drives offer similar storage capacities as entry level internal drives but are limited to capacities less than 200 GB at most due to the structural limitation of the drive. Due to the smaller size, the number of storage platters as well as the magnetic density of these platters, these drives cannot go beyond certain limitations. Though, developments are in progress to increase storage densities. The perfect choice for frequent travelers, external drives function as backup devices or replacement to CDs and floppies for large amounts of data.

• IDE / ATA (back to top)

The acronym stands for Integrated Drive Electronics / AT Attachment, and is the most common interface adopted by most motherboard chipset manufacturers in the world. Being highly cost effective and simple to implement, configure and use, the interface has gained wide acceptance by most users and system integrators around the world. Though this interface is quite fast for data transfer, it doesn't match the speeds offered by other competing standards developed by various other engineering organizations. The interface features a 40 pin, 80 conductor flat ribbon wire that connects to the drive on one end and to the mother board on the other end. It has a maximum rated speed of 100 MB/s with a few exceptional companies stating 133 MB/s of data transfer rate. Most hard drives, CD-Rom, DVD-Rom, CD Writer/ Re-writer, and DVD-Writer drives are available sporting this interface.

 

• SCSI (back to top)

The oldest of them all, the Small Computers System Interface (SCSI), pronounced as "Scuzzy" was the first one to be developed to facilitate data to be stored on non-volatile fixed memory devices. The earliest known form was implemented in the initial floppy drives. Later on, with the development of hard disk drives, the interface became the de facto standard to be implemented in most Apple Macintosh computers, Sun Ultra Sparc series, high end servers, mainframes, etc. The SCSI interface was abandoned by the industry as an integrated feature on the mother board by the advent of the newer ATA/IDE interface due to the latter's cheaper production and implementation costs. Industry professionals and engineers continued its development with faster and faster transfer rates offered every couple of years, the SCSI standard is yet the most sought after interface for professionals requiring high data throughput such as data servers, multimedia professionals, animation artists, movie sound and visual effects editors, etc. The current rate of data transfer offered by a SCSI bus drive stands at a 320 MB/s using the latest Ultra 320 SCSI drive interface and special add-on cards. Custom manufactured motherboards may be available sporting this interface integrated onto the motherboard itself it may prove to be a costly affair. The various versions of SCSI available in the market are Fast SCSI, Fast-Wide SCSI, Ultra SCSI, Ultra Wide SCSI, Ultra2 SCSI, Ultra2 Wide SCSI, Ultra3 SCSI, and Ultra-320 SCSI. The standards vary according to each other in terms of connectivity as well as data transfer rates, starting with the initial, now outdated, Fast SCSI interface capable of 10 MB/s and the latest Ultra-320 SCSI capable of delivering 320 MB/s. the notable interfaces would be Ultra2 Wide SCSI providing 80 MB/s of sustained data transfer rate and the Ultra3 SCSI giving 160 MB/s of transfer rate.

 

• Serial ATA or SATA (back to top)

Developed in early 2000, the Serial ATA or SATA interface is a successor to the older ATA interface, now retroactively renamed to PATA or Parallel ATA. The first generation of the interface uses serial attachment and retrieval method of transferring data between the hard drive and the motherboard. It was developed as an answer to the constraints cropped up in the further development of any faster PATA interfaces and devices. This interface is relatively simpler to manufacture, implement and use along with providing excellent data transfer rates. The first generation standard called the SATA 1. 5 Gbits/s offers speeds up to 150 MBytes/s with the second generation called the SATA 3. 0 Gbits/s offers 300 MBytes/s. the yet in development third generation SATA 6. 0 GB/s can attain 600 MB/s of data transfer rates.

 

 

3. Purchasing Criteria (back to top)

With the various types of drives that can now be easily identified, "which drive do I buy?"is the first question that pops up. Apart from the different interfaces sporting different speeds, hard drives come in different capacities. Starting from a lowly 20 GB of storage space, the most top end drives can pack in as much as 1 Terabyte of data. The following criteria will help in deciding which drive is right for you.

• Capacity (back to top)

For a regular user using a simple operating system such as Windows and some office suites along with a couple of games, music and videos, any drive containing at least 10 GB and up to 100 GB of capacity will suffice. For someone in the graphics profession would normally require a drive with a capacity of 100 GB to 400 GB, due to the size of the working files. For a multimedia enthusiast a minimum of 300 GB and above should be opted for.

 

• Speed of Data Transfer (back to top)

With high performance interfaces being developed, the internal mechanics of a drive need to keep up with the speed in order to achieve maximum bandwidth utilization. The rotating spindle driven by the servo motors maintain a steady speed by feeding the interface with a continuous flow of data. The servo motors spin at different speeds, implemented across all types of interfaces. Though each speed is best suited to a particular type of user, any category of user can at any given time opt for a drive slower or faster than his requirements. For the regular user, a drive with a 5,400 RPM to 7,200 RPM should be sufficient for everyday use. Graphics editors and multimedia professionals normally require a drive with a minimum of 7,200 RPM and up to 15,000 RPM.

 

• Interface Type (back to top)

The simpler ATA/IDE interface is mostly suited to regular desktop users or networked computers on corporate network. The SCSI interface is most suited to extremely demanding applications such as Internet servers, email servers, file servers, data centre servers, backup servers, etc. Multimedia professionals who need real-time rendering of animation projects or sound effects manipulation may also opt for such high performance drives. For desktop graphics artists or editors, certain entry level SCSI drives as well as SATA drives will cater to most graphics application needs. A user should review his/her needs, along with considering the future growing demands of applications and data requirements before ascertaining the exact type of disk drive.

 

• Seek Time (back to top)

As with internal rotational speeds of the drive mechanisms, the head of the drive should move with enough speed to locate the data on the disk surface. The time taken for the head to make its way to the area of relevant data is known as the 'seek time'. Thus, a drive with a lower seek time is preferable. Drives with high seek times are not beneficial to disk spindles rotating at higher RPMs, such as 7,200 RPM. Hence, with a very fast interface coupled with a very fast RPM rate, a drive should have the lowest seek time. A good seek time is usually around 5ms to 6ms (milliseconds). Entry level drives generally have a seek time of about 8ms, while high performance drives can do 4 ms.

 

• Cache Memory (back to top)

Any hard drive has an internal buffer area that holds the data read from the disk surface before transferring it to the transfer interface bus. This area known as the Cache memory is a high speed memory which is costly to manufacture and implement. Hence, it is scarcely implemented into the drive mechanics. This size of implemented memory makes a lot of performance difference when executing high bandwidth applications such as multimedia software or data server requests.

 

The average amount of cache memory is around 512 kilobytes. High speed and high capacity drives can have as much as 8 MB of cache memory to supplement the drives faster speed while it is locating data. Any drive, or especially the SCSI and SATA range of high performance drive, should at a minimum have a 1 MB to 2 MB of cache memory. Entry level drives of lower capacity running at a lowly 5400 RPM may have only 512 KB or 256 KB of cache.

 

• Internal or External(back to top)

Choosing between an internal external drive depends on the use of the device. Under everyday processes such as running the operating system, gaming or even storing huge amounts of data, an internal drive would be the obvious choice. An internal drive, though it is a tiny device, doesn't offer any portability due to the complexities involved in implementing and configuring the drive for usage. Whereas, an external drive is purely intended to provide absolute plug-and-play use via either the USB or a FireWire interface. An external drive upon connecting with the base CPU unit shows up as an actual external drive, though the actual drive and its partitions would show up as local partitions.

 

 

4. Making the Decision (back to top)

After deciding upon your requirements, you should compare various drives that match those specs at a comparison shopping site such as www.smarter.com. You can compare prices and features across various drives while confirming their compatibility with your PC. You may also check with multiple suppliers on the Internet for feature comparisons and user reviews for first hand experiences with a particular model.

While purchasing a drive, the most important criteria to be focused upon should always be the available speed and capacity of the drive. For a given category of a user, a drive should not offer higher storage capacity at slow speeds. Higher storage capacity drives are usually much slower due to their higher seek times. Hence, such drives should have a higher RPM as well as sufficient cache memory to offset the potentially high seek time of the drive. In any drive, capable of extremely high data transfer rates, the storage capacity should not take a back seat at a given cost.

Buying the right hard drive requires investment of a reasonable amount of time in researching and evaluating the various contenders. The trick is to strike the perfect balance between price and functionality and the best way to begin is to find out exactly what your needs are. Hopefully now you have more information to help make your purchasing decision more informed, now go find a great hard drive!