Guide: The difference between SSDs and HDDs


This guide outlines the main differences between solid state drives (SSDs) and hard disk drives (HDDs).

There are two major types of SSD in current production — NAND and DRAM. This guide focuses on the more common one: NAND.

It’s worth noting that advances are being made all the time on both types of drive and that these differences are generalisations. Individual performance will vary from manufacturer to manufacturer.

1. Speed

Most solid state drives, except ones made using cheaper components, are significantly faster at reading data than a hard drive.

This is because there are no moving mechanical parts on a SSD and so the “seek time” is significantly reduced. Incidentally, DRAM drives are faster still.

Writing large files is also generally quicker on a SSD, though at present there are often performance problems when trying to write a lot of small files to a SSD. It’s possible to overcome this through improved system design.

In general, though, SSDs are faster than HDDs.

(PS: SSDs are generally quieter than HDDs because they don’t have any moving parts and are usually fanless)

2. Cost

At present, SSDs are much more expensive than an equivalent capacity HDD, although the price is gradually coming down.

Cost per GB of a SSD can be four to eight times as much as the cost per GB of a hard drive.

3. Reliability

In fairness, both types of technology are extremely reliable.

Hard drive technology is mature and failures are rare, though solid state drives can operate reliably in harsher environments, primarily because they have no moving parts, and have a better “mean time between failures” rating.

It’s worth noting, however, that SSDs are still a very young technology and as such overall reliability levels are yet to be fully proven.

Another interesting fact is that most solid state drives fail when data is being written to them, while most hard drives fail when data is being read.

If a drive fails when data is being written, the computer’s operating system can simply attempt to write the data elsewhere. If a drive fails when data is being read, it’s likely that the data has been lost/corrupted.

4. Capacity

Hard drives still have the edge in storage capacity, with 1TB+ drives readily available to consumers.

SSDs have only started pushing the 256GB mark, with 512GB capacities becoming available and a 1TB version in testing.

Of course, it’s possible to link more than one drive of either type together in a system to increase overall system storage.

5. Lifespan

Notwithstanding a crash, hard drives may have a longer lifespan, because SSDs have a finite number of times each “cell” can be written to. Then again, the mechanical parts of a hard drive will wear out over time – a problem SSDs don’t have.

For most users, the lifespan of both types of drive will be good – easily several years or more unless you’re extremely unlucky!


For the average computer user, hard drives remain a perfectly good option.

They’re much cheaper, pretty reliable, with plenty of options and capacities for use as internal or external drives, main or backup media.

SSDs are great if you’re doing a lot of time-critical work such as video editing, music making, and such like, because they can replace one of the major bottlenecks – the speed of reading and writing data to disk.

However, they are still very expensive and as yet aren’t a fully proven technology. Fewer manufacturers are currently producing them.

Another option is to get a hybrid drive or a system with a lower-capacity SSD and a large, main hard drive. Certain functions, such as booting up the system, get a speed boost from the SSD but you still have high capacity, low cost storage from the hard drive.

Advice: stick with hard drives unless you’ve got the money and the need to use solid state drives.

Give it another couple of years and things might be different.

Andy Merrett


  • Elementary, my dear Watson…!!

    Sorry, but this is just rudimentary junk. I was looking for more than a set of generalized statements – like benchmarks, do SSDs even performance throughout the disk etc…

  • This is such a great resource that you are providing and you give it away for free. I love seeing websites that understand the value of providing a quality resource for free. Thanks.

  • i think you forgot to mention the size ,the ssd are much smaller compared to the HD which makes them to be adapted for notebooks ,mobile devices

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