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Guide to buying Hard Drives

Apart from being one of the most essential parts of your computer, hard drive storage is constantly updating, in terms of both capacity of disk space and in physical size. When it comes time to upgrade your disk storage, there are a number of factors for you to take into account. Once you've made basic decisions about size, connectivity, speed and data transfer rate, and whether you want an internal drive or external.

How A Hard Drive Works

Your hard drive has a number of magnetized platters connected to a spindle. The spindle spins the platters at a very fast speed while a series of read/write heads scan over them both looking for and writing information. This information is transferred via a cable system, or through a wireless connection to a hard disk controller, which in most systems is built into the motherboard, or in some systems installed as an add-in card. The information that comes from your hard drive through its controller is then made available to the components of your computer. The effectiveness of your hard drive (its performance) depends on how much of its capacity remains unused, how well organized the data is (known as fragmentation) and its data transfer rate, which in turn is dependent on its connection type and the drive's spin rate.

Internal Hard Drives

Most computers from, the most basic home models up to the most powerful servers, have an internally installed hard drive. Technology today ensures that they are all generally fast, reliable, and offer dependable storage ability. Most modern computers have installation slots and cabling to enable you to install additional hard drive. This allows you to increase your storage capacity without giving up your existing hard drive.


External Hard Drives

These drives are essentially the same drives as ones installed inside computers, but cased inside a protective, portable case. This is a good solution for people who work remotely and need to transport large amounts of data. If an external hard drive is your choice, make sure your computer is compatible with the interface that the hard drive uses. An add-in card, such as a FireWire card can help to increase your computer's capabilities.

Laptop Hard Drives

There have been many advances in miniaturization of hardware components for laptop computing, and hard drive technology is not left out of this loop. Laptop hard drives function in exactly the same way as internal hard drives on other computers, only they are designed to provide maximum storage and efficiency in the smallest possible package. For added flexibility, some laptop computers come with removable hard drives that can be easily installed and removed. However, before you buy a hard drive for your portable computer, check that the hard drive's specifications will meet the standards of your computer, as many laptop hard drives are proprietary, and are not compatible with other brands and models.


Size

Your hard drive stores your operating system, its programs (games and applications), your working data, and your digital music and movies. Most new computer purchases have a minimum of 80 GB of hard disk space; many have considerably more. Hard drive space is one of those things, once you have it, you'll find ways to fill it soon enough. There is no real rule of thumb, but consider the cost per gigabyte of storage as a way to guide your purchase. If you work with large files, such as music, video and graphics, it pays to have a big storage space for your work. It may pay you to have two hard drives, one that houses all your programs and applications, and another for storing your work and projects.

You may want to compare the price of say a 160GB drive against two separate 80 GB drives. If one drive fails all is not lost. Today's hard drives however, are fairly robust pieces of equipment and providing they are not abuse, will serve you well for a long period of time.

Interface

One key distinguishing factor between hard drives is the way in which they connect to your computer. There are a number of basic types of connection schemes used with hard drives. Each connection type has a range of differences in performance.

IDE (INTEGRATED DRIVE ELECTRONICS)

This is by the most common connection methods. Because the hard drive controller is on the drive itself rather than on the motherboard, it helps to keep costs down. There different IDE standards available. Mostly, you will want to purchase the fastest possible standard that your computer can support. Most computers will support a standard that is faster than what the computer currently supports, so you can buy a faster drive, and update your computer at a later time. The different IDE standards, in order from most basic to fastest, are:

 
  • ATA (Basic). Supports up to two hard drives and features a 16-bit interface, handling transfer speeds up to 8.3 MB per second.

     
  • ATA-2 or EIDE (Enhanced IDE). Supports transfer speeds up to 13.3 MB per second.

     
  • ATA-3. A minor upgrade to ATA-2 and offers transfer speeds up to 16.6 MB per second.

     
  • Ultra-ATA (Ultra-DMA, ATA-33 or DMA-33). Dramatic speed improvements, with transfer rates up to 33 MB per second.

     
  • ATA-66. A version of ATA that doubles transfer rates up to 66 MB per second.

     
  • ATA-100. An upgrade to the ATA standard supporting transfer rates up to 100 MB per second.

     
  • ATA-133. Found mostly in AMD-based systems (not supported by Intel), with transfer rates up to 133 MB per second.


    SCSI (SMALL COMPUTER SYSTEM INTERFACE)

    This is the hard drive interface standard used by many high-end PCs, networks and servers, and Apple Macintosh computers, except for the earliest Macs and the newer iMacs. While some systems support SCSI controllers on their motherboards, most feature a SCSI controller add-in card. SCSI drives are usually faster and more reliable, and the SCSI interface supports the connection of many more drives than IDE. While SCSI drives come in many different standards, many of them are not compatible with one another. So it's important be know that your computer supports the drive you plan to install. The different SCSI connections are:

     
  • SCSI-1. A basic connection using a 25-pin connector, supporting transfer rates up to 4 MB per second.

     
  • SCSI-2. Uses a 50-pin connector and supports multiple devices with a transfer rate of 4MB per second.

     
  • Wide SCSI. These drives have a wider cable and a 68-pin connection that supports 16-bit data transfers.

     
  • Fast SCSI. Uses an 8-bit bus but transfers data at 10 MB Per second.

     
  • Fast Wide SCSI. Doubles both the bus (16-bit) and the data transfer rate (20 MB per second).

     
  • Ultra SCSI or Ultra Wide SCSI. Uses an 8-bit bus and transfers data at 20 MB per second.

     
  • SCSI-3. Features a 16-bit bus and transfers data at 40 MB per second.

     
  • Ultra2 SCSI. Uses an 8-bit bus and transfer data at a rate of 40 MB per second.

     
  • Wide Ultra2 SCSI. Uses a 16-bit bus and supports data transfer rates of 80 MB per second.



    FIREWIRE (IEEE 1394)

    The FireWire standard is becoming popular in portable hard drives because it can be connected and removed without having to reboot the computer. It supports data transfer rates of 50 MB per second, which means it is ideal for video, audio and multimedia applications. FireWire requires a dedicated add-in card and the hard drives in use require an external power source, but the interface can support up to 63 devices simultaneously.


    USB 1.1 (UNIVERSAL SERIAL BUS)

    Pretty much all computers today include USB ports on their motherboards. (On older model, you can install an add-in card.) USB controllers can be used to connect external hard drives, and can support as many as 127 devices simultaneously either through USB port hubs or linked in a daisy chain fashion. USB controllers do delivery power to devices connected to them, but many hard drives still use an external power source. USB is limited by its data transfer speed, the maximum rate being about at 1.5 MB per second.


    USB 2.0 (HI-SPEED USB)

    A more recently introduced and far better connection standard that offers backward compatibility and data transfer rates of up to 60 MB per second. USB 1.1 system can use a USB 2.0 device; it will need a USB 2.0 controller card to achieve the higher transfer rates.


    FIBRE CHANNEL

    Fibre Cabling is mainly used for high-bandwidth network servers and workstations, providing very fast data transfer rates (up to 106MB per second), and connection at long cabled distances, although it is expensive and you need to install a special interface card.

    Spin rate

    Data transfer rate is crucial to how well your computer performs for you. Apart from the connection types above, the performance of your hard drive depends on its spin rate, measured in RPM. Higher RPM generally means faster data transfer rate. The lowest spin speed that is acceptable in computing today is 5400 RPM. The common standard at present is 7200 RPM. But higher speeds are available in SCSI drives, and it is one area of computer system technology that is constantly being developed.

    A larger capacity hard drive will not necessarily make your system function any faster unless you are low on available disk space with your existing drive. But a drive with Ultra ATA/100 or ATA/133 and a 7200 RPM spin rate will pretty much guarantee an improved hard drive performance.


    CACHE

    Cache (pronounces 'cash') is additional temporary memory that acts as a buffer between the system and the drive. Frequently accessed data is stored in the cache for quick access. Cache sizes vary from 512 KB up to 16 MB on some SCSI drives. The larger cache you have on your drive, the faster your drive will transfer data. If you are working with large files, such as video, images and audio files, it pays to have the largest cache you can get (8MB or more).

    SEEK TIME

    The data on your disk is stored in tracks and sectors and when you instruct your hard drive controller to retrieve some data, it goes looking. The seek time is a measure of how long it takes the hard drive to find a specific track on a disk. Seek times can vary slightly from disk to disk and a drive with a faster seek time will always perform better.

    INTERNAL AND EXTERNAL TRANSFER RATES

    These two rates tell how fast a drive actually reads the data and passes it along to the system. Internal Transfer Rate refers to the time it takes for a drives heads to read data from the platter and pass it to the drive's cache. The External Transfer Rate (sometimes called the Transfer Rate or the Burst Transfer Rate) is a measure of the time it takes to send the data from the cache all the way to the computer's memory. Naturally faster transfer rates provide better performance.

    S.M.A.R.T. (Self-Monitoring Analysis and Reporting Technology)

    This is a nice built-in feature in some hard drives that can help alert you to a potential hardware problem. Your computer's BIOS must support this in order for the SMART function it to work, however the drive itself will still work in a system without it.
     
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