External hard drives provide the greatest storage space for the money. Here are the basic technical specifications you need to look at to decide which drive is the best value for the money:
Whichever drive you select, it needs to be large enough to hold all the data you intend to store on it, plus some extra for ‘growth’. Usually, this is the total of all the data you intend to copy to the drive, doubled or tripled, depending on how fast you add data to the drive. These days, storage is cheap and opting for the larger drive won’t hurt your wallet too much.
The total storage space of any hard disc drive is measured in bytes. Even the smallest hard disk drives available today will hold hundreds of millions of bytes (MB). Unfortunately the latest version of windows needs tens of billions of bytes (roughly 20 GB) just to function properly. Storage space for current external drives is measured in one of the following values.
From smallest to largest, where larger is better:
There is a measurement beyond petabytes; however, there are no petabytes sized drives yet, and petabyte at drives probably will not be available commercially for at least a few years. MB are smaller than GB which in turn are smaller than terabytes (TB). The largest drives available today (2010) are 1.5 to 2 TB. The larger the storage space the greater the cost of the drive.
To compare two drives on the basis of cost per storage, you need to calculate the value of how much storage every dollar buys you. This ratio is simply the cost of the drive divided by the total storage space. The easiest calculation is to figure out how much each gigabyte costs by dividing the cost of the drive by the number of gigabytes on the drive. Terabyte drives have 1024 Gigabytes per Terabyte and 1024 Megabytes per Gigabyte. Those numbers will seem weird unless you know that computers use base-2 math and humans use base-10 math. The easiest way to figure out the cost per Gigabyte is to round off to an even 1000 GB per Terabyte for cost comparisons to make the math easy. Usually, when you get a lot more storage for the money, its because they used fewer, or slower connections, less cache memory, or a slower spindle speed
Here’s the math for two example drives. The smaller drive in this example would be the better value based on storage space, but always consider spindle speed, cache memory size and the connector bus type.
$100 / 500 GB drive = $0.20 per GB
$250 / 1024 GB (1 TB) drive = $0.24/GB
So now, it’s on to spindle speeds.