How to Choose and Buy Hard Disk Drives

Are you buying a HDD? Then learn how to choose and buy hard disk drives that don't just perform better, but cost less as well.

HDD Capacity - How Much Hard Disk Space Do You Need?

Your HDD is first and foremost a storage device, so buying a hard disk drive with enough space is crucial. To help you out, here are some average file sizes:

  • Windows 8 - 20 GB
  • Windows 7 - 20 GB
  • Apple OS X - 8 GB
  • Microsoft Office - 3 GB
  • 2 Hour Movie (DVD quality) - 800 MB
  • 2 Hour Movie (Full HD quality) - 4GB
  • JPEG Photo - 3 MB
  • MP3 Song - 4 MB

When you buy hard disk drives, have you ever noticed that it always comes with less space than advertised? For example, you buy a 1,000 GB (1 TB) HDD and instead showing up as 1,000 GB in Windows Explorer, you end up only having 930 GB of storage space.

This happens because hard drive manufacturers assume that 1 kB = 1000 bytes, while your operating system recognizes 1 kB = 1024 bytes. Take-home lesson of the day: When you buy a HDD, your actual hard disk space will be about 7% less than the advertised numbers.

To avoid slow downs and fragmentation problems, you will also need to leave at least 15% of your hard disk empty.

So taking everything so far into account... Assuming that you're going to need 800 GB to store all your files, then you should buy hard disk drives with at least 1 TB capacity.

HDD Speed - What Affects Your HDD Performance?

We have already covered this topic in detail in our Hard Disk Speed - What Affects Hard Disk Performance article, so let's have a summary of the important findings here:

HDD speed is dictated by two factors: RPM (platter rotational speed) and data density (number of platters).

Consumer hard disk drives come in three rotational speeds: 10,000 RPM, 7,200 RPM, 5,400 RPM

10,000 RPM drives are the speed kings of the bunch, but they have fallen from grace in recent years due to the growing popularity of solid state drives. If hard drive performance is essential to you, then we recommend that you buy a solid state drive since they offer better value for money (tremendous speed gains at moderate price premiums over 10,000 RPM drives).

7,200 RPM are our recommended choice for most mainstream users since they provide a good balance of respectable performance and cheap storage, making them ideal for a budget boot drive and general-purpose use.

What 5,400 RPM drives lack in speed... they make up for it in lower power consumption, lower temperatures and quieter operations. This makes them appealing in situations that don't really benefit the higher speeds of 7,200 RPM drives, such as media storage (videos, images and audio files) or for use in a NAS (multiple speed bottlenecks).

Always choose hard disk drives with the least number of platters (at your preferred capacity and RPM). All other things being equal, hard disk drives with less data platters are going run faster and cooler.

HDD Reliability - What is the Most Reliable HDD Brand?

Which hard disk drive brand and model is the most reliable? If you're buying hard disk drives, chances are that you would have wondered about this question...

  • No large-scale independent study on hard disk brand reliability has ever been published - Google published a famous research paper on hard disk failures in 2007, but no brand or model was mentioned in their paper.

  • Russian data recovery firm did publish a study which suggested that Hitachi drives were the most durable while Seagate drives suffered the highest failure rates... but given its small sample size of 4,000 hard disk drives, we would suggest you view their results as an interesting read rather than hard facts.

  • If you prod through tech forums and customer reviews, you will find that everyone has their own favorite brands... and there is no clear winner among the major manufacturers.

Since buying a HDD by brand is essentially a big gamble, so what can you do to buy hard disk drives that are going to more reliable?

  • Buy hard disk drives with longer warranties. Most hard disk drives come with two to five year warranties.

  • Buy hard disk drives that operate at lower temperatures, such as drives with lower RPM and fewer number of platters - See our article on HDD temperature for more details.

  • Do a quick search on popular tech forums and consumer reviews to see if there are any major flaws and complaints with the particular HDD brand and model that you're buying.

And no matter how rock-solid your hard disk drive is, always back up your data regularly. There is just no substitute for an old school data back-up.