Choosing a Hard Disk

The storage space on your PC, the permanent residence of your programs, applications, and data, is needless to say, a matter of careful thought and selection.

The choice of hard disk will depend on the size you require, your budget, and the factors that affect its performance.

Where size is concerned, bigger is usually better. 8 GB hard disks have become entry level. If you need to run common productivity applications, browse and download stuff from the Web, and play games, this should be enough for you. But you’ll need a larger hard disk if you’re heavily into gaming and multimedia, with all the latest games loaded on your PC. Or, if you do high-end graphics, CAD/CAM or multimedia work, you would again be advised to go in for a larger disk. With prices of hard disks on a downswing, you should be able to get a large and fast hard disk that suits your pocket too. For example, the Seagate U8 17.2 GB hard disk costs just Rs 8,350.

The next thing to consider is the speed. To understand the various measures of disk speed, we need to understand how a hard disk works. A hard disk is made up of round, flat disks called platters, which are coated on both sides with a special material that stores data in magnetic patterns. Each platter has data stored in concentric circles called tracks, and each track is divided into smaller pieces called sectors, with each sector holding 512 bytes of data. These platters have a hole in the center and are mounted on a spindle. They rotate at high speeds, driven by a motor connected to the spindle. To read information from or record information on these platters, electromagnetic devices called heads are used. Their position on the disk is controlled by a device called the actuator. 

The hard disk also has a logic board, which controls the activity of the other components and interacts with your PC. On this logic board sits an internal buffer or cache, which holds the data that was recently accessed from the disk, and data that is likely to be asked for in the near future. A larger cache is usually better, because it can store more data, thereby improving performance, since the data doesn’t have to be fetched from the hard disk all the time. So, all other things being the same, go for a disk with a larger cache.

The performance of the hard disk thus depends on various factors, such as the seek time, latency, access time, spindle speed, etc.

Seek time The amount of time required for the read/write heads to move between tracks. This is measured in milliseconds, and the lower the seek time, the better.

Latency The speed at which the hard disk platters spin is usually faster than the speed at which the read/write heads move to a particular sector where the information that you’ve asked for is stored.

Latency is the time for which the drive has to wait for the correct sector to come around to where the read/write heads are waiting for it. This is also measured in milliseconds, and the faster the speed at which the platters rotate, the lower the latency.

Access time This is based on the seek time and latency of the hard drive.