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Replacing Hard Drive

Planning Ahead: External Hard Drive Backup

When itÂ’s time to decide on replacing hard drive, or to install new hard drive, you need to understand capacity and speed of hard drives (e.g. gigabyte or terabyte hard drive). You also need to develop an external hard drive backup plan (before you need it); this would include hard drive data recovery services and/or hard drive repair software.


What You Need to Know When Replacing Hard Drive:

Understand Hard Drive Capacity

How A Hard Drive Works

If you are replacing hard drive in your system, consider your capacity and speed needs: have they increased? Do you need to upgrade? To figure out the capacity of a hard drive, you multiply the number of cylinders by the number of heads by the number of sectors, by the number of bytes/sector (usually 512).

Or, you just look at the label and see that it has a capacity of 120GB. Of course, you have probably noticed that in Windows, you see a different size reported for the size of your drive. There is a good reason for this.

Hard drive manufacturers and your operating system use two different forms of measurement, and both happen to be correct.

Windows uses binary measurement, and the manufacturer uses decimal measurement. To see the differences here, we have to look at binary numbers compared to decimal numbers. Remember that binary numbers are a power of 2, and decimal a power of 10.

  • The binary number 2^10 = 1024, and the closest decimal equivalent is 3^10, or 1000.
  • The binary number 2^20 = 1,048,576, and the closest decimal equivalent is 10^6, or 1,000,000.
  • The binary number 2^30 = 1,073,741,824, and the closest decimal equivalent is 10^9, or 1,000,000,000.
  • The binary number 2^40 = 1,099,511,627,776 and the closest decimal equivalent is 10^12 or 1,000,000,000,000.

Now, look also at the prefixes used to describe data sizes.

  • Kilo = 1 Thousand
  • Mega = 1 Million
  • Giga = 1 Billion
  • Tera = 1 Trillion

So if we take these numbers and divide them we get the following:

  • 1000/1024 = .977
  • 1,000,000/1,048,576 = .954
  • 1,000,000,000/1,073,741,824 = .931
  • 1,000,000,000,000 / 1,099,511,627,776 = .910

This is one of the quirks with how a hard drive works. As you can see, the more data you are measuring, the greater the discrepancy. When you get to the Terabyte hard drive level, as the latest drives are, you get a discrepancy of 9%. That's going to be quite a difference. So to be correct here, Windows is actually reporting the incorrect size.

Windows uses binary calculations, and then puts the GB next to it, when technically that is not correct according to the definition of Giga. Although this confuses things, don't expect the manufactures to change, and do you think Windows will change? But on the flip side, would you rather see the drive sold as a 2^40 byte drive, or a 1 Terabyte hard drive? Just keep in mind that the drive you buy will be the advertised size, Windows just shows it differently.


Understand Hard Drive Speed

Finally, let's take a look at read and write speeds. The speed of the hard drive is reported RPMs, or revolutions per minute. This is a measure of the speed that the platter is spinning at. The faster the revolution, the more data passes beneath the read/write head. The faster it spins, the more data can be delivered or written within a specific timeframe.

Most desktop hard drives today spin at 7,200 RPM, and the average laptop hard drive spins at 5,400 RPM. 10,000 RPM drives are available for desktops from Western Digital, but they are going to cost significantly more. You can get a 500GB 7,200 RPM drive for the same price as a 150GB 10,000 RPM drive.

A laptop hard drive is also available at 7,200 speeds, but because they consume more power, they are not the norm. Depending on your use of the laptop, when you purchase be sure to check the drive speeds. If you are doing any gaming or software development, you will want to go with the 7,200 speed drive. Also keep in mind, that even when you are purchasing a high end laptop, you should check the drive speed as the default for almost all laptops is 5,400 RPM drives.


Install New Hard Drive

If you are interested in learning how to install a hard drive, check out this article or if you want to find out more about how a hard drive works, then check out this article.

And, make sure that whether you are replacing hard drive or installing a new hard drive, that you plan ahead and do regular backups (use an external hard drive backup system), have hard drive repair software and/or hard drive data recovery services readily available in case of a hard drive crash.

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