difference between SSD and HDD

SSD vs HDD

Most people now buy laptops for their computing needs and have to make the decision between getting either a Solid State Drive (SSD) or Hard Disk Drive (HDD) as the storage component. So which is best to get, an SSD or HDD? There’s no straight-forward answer to this question; each buyer has different needs and you have to evaluate the decision based on those needs, your preferences, and of course budget. Even though the price of SSDs has been falling, the price per gigabyte advantage is still strongly with HDDs. Yet, if performance and fast bootup is your primary consideration and money is secondary, then SSD is the way to go. We’ll make a comparison of SSD and HDD storage and go over the good, the bad, and the ugly of both.

What is an SSD?

We’ll make no assumptions here and keep this article on a level that anyone can understand. You might be shopping for a computer and simply wondering what the heck SSD actually means? To begin, SSD stands for Solid State Drive. You’re probably familiar with USB memory sticks - SSD can be thought of as an oversized and more sophisticated version of the humble USB memory stick. Like a memory stick, there are no moving parts to an SSD. Rather, information is stored in microchips.  Meanwhile, a hard drive uses a mechanical arm with a read/write head to move around and read information from the right location on a storage platter. This difference is what makes SSD so much faster. As an analogy, what’s quicker? Having to walk across the room to retrieve a book to get information or simply magically having that book open in front of you when you need it? That’s how an HDD compares to an SSD; it simply requires more physical labor (mechanical movement) to get information.

A typical SSD uses what is called NAND-based flash memory. This is a non-volatile type of memory. What does non-volatile mean you ask? The simple answer is that you can turn off the disk and it won’t “forget” what was stored on it. This is of course an essential characteristic of any type of permanent memory. During the early days of SSD, rumors floated around saying stored data would wear off and be lost after only a few years.  Today this is not true; you can read and write to an SSD all day long and the data storage integrity will be maintained for well over 200 years. In other words, the data storage life of an SSD can outlive you!

An SSD does not have a mechanical arm to read and write data, it instead relies on an embedded processor (or “brain”) called a controller to perform a bunch of operations related to reading and writing data. The controller is a very important factor in determining the speed of the SSD. Decisions it makes related to how to store, retrieve, cache and clean up data can determine the overall speed of the drive. We won’t get into the nitty-gritty details for the various tasks it performs such as error correction, read and write caching, encryption, and garbage collection to name a few. Yet, suffice to say, good controller technology is often what separates an excellent SSD from a simply good one. An example of a fast controller today is the SandForce SATA 3.0 (6GB/s) SSD controller that supports burst speeds up to 550MB/s read and write speeds.

Finally, you may be wondering what an SSD looks like and how easy it is to replace a hard drive with an after-market device. If you look at the images below you’ll see the top and undersides of a typically-sized 2.5” SSD. The technology is encased inside either a plastic or metal case and looks like nothing more than a battery might:

TOP Top Side

SSD Bottom Side

The form factor of the SSD is actually the same as a regular hard drive. It comes in a standard 1.8”, 2.5”, or 3.5” size that can fit into the housing and connectors for the same-sized hard drives. The connector used for these standard sizes is SATA. There are smaller SSDs available that use what’s called mini-SATA (mSATA) and fit into the mini-PCI Express slot of a laptop.

What is an HDD?

Hard Disk Drives, or HDD in techno-parlance, have been around for donkey's years relative to the technology world. HDDs were first introduced by IBM in 1956 - yes folks this is nearly 60-year old technology, thank goodness vacuum tubes for TVs didn’t last so long! An HDD uses magnetism to store data on a rotating platter. A read/write head floats above the spinning platter reading and writing data. The faster the platter spins, the faster an HDD can perform. Typical laptop drives today spin at either 5400 RPM (Revolutions per Minute) or 7200RPM, though some server-based platters spin at up to 15,000 RPM!

The major advantage of an HDD is that it is capable of storing lots of data cheaply. These days 1 TeraByte (1,024 gigabytes) of storage is not unusual for a laptop hard drive, and the density continues to grow. Cost per gigabyte is only around $0.075/GB these days for an HDD (based on buying a 4TB model), amazing when you compare it to the $1.00/GB cost for an SSD (240GB model) . If you want cheap storage and lots of it, using a standard hard drive is definitely the more appealing way to go.

When it comes to appearance, HDDs essentially look the same from the outside as SSDs. HDDs predominantly use SATA interface. The most common size for laptop hard drives is the 2.5” form factor while a larger 3.5” form factor is used in desktop computers. The larger size allows for more platters inside and thus more storage capacity. Some desktop hard drives can store up to 4TB of data! Below is an example of what an HDD looks like using the Seagate Barracuda 3TB hard drive:

HDD Top Side

HHD Bottom Side

SSD Vs HDD Comparison

Now it’s time to do some comparisons and determine which might be best for your individual needs - SSD or HDD?  The best way to compare items is a table with a side by side comparison of items in which a green box indicates an advantage:

Attribute	SSD (Solid State Drive)	HDD (Hard Disk Drive)
Power Draw / Battery Life	Less power draw, averages 2 – 3 watts, resulting in 30+ minute battery boost	More power draw, averages 6 – 7 watts and therefore uses more battery
Cost	Expensive, $1.00 per gigabyte (based on buying a 240GB drive)	Only around $0.075 per gigabyte, very cheap (buying a 4TB model)
Capacity	Typically not larger than 512GB for notebook size drives	Typically 500GB – 2TB for notebook size drives
Operating System Boot Time	Around 22 seconds average bootup time	Around 40 seconds average bootup time
Noise	There are no moving parts and as such no sound	Audible clicks and spinning can be heard
Vibration	No vibration as there are no moving parts	The spinning of the platters can sometimes result in vibration
Heat Produced	Lower power draw and no moving parts so little heat is produced	HDD doesn’t produce much heat, but it will have a measurable amount more heat than an SSD due to moving parts and higher power draw
Failure Rate	Mean time between failure rate of 2.0 million hours	Mean time between failure rate of 1.5 million hours
File Copy / Write Speed	Generally above 200 MB/s and up to 500 MB/s for cutting edge drives	The range can be anywhere from 50 – 120MB / s
Encryption	Full Disk Encryption (FDE)Supported on some models	Full Disk Encryption (FDE) Supported on some models
File Opening Speed	Up to 30% faster than HDD	Slower than SSD
Magnetism Affected?	An SSD is safe from any effects of magnetism	Magnets can erase data

If we tally up the checkmarks, the SSD gets 9 and HDD gets 3. Does that mean the that an SSD is three times better than an HDD? Not at all. As we mentioned earlier, it all depends on individual needs. The comparison here is just to lay out the pros and cons for both options. To aid you even more, here are some rules to follow when you decide which drive is best for you:

• You need lots of storage capacity, up to 4TB
• Don’t want to spend much money
• Don’t care too much about how fast a computer boots up or opens programs - then get a hard drive (HDD).

• You are willing to pay for faster performance
• Don’t mind limited storage capacity or can work around that - then get a solid state drive (SSD).

Today it still makes sense for a majority of typical buyers just to get an HDD inside a new computer simply due to the much cheaper cost. However, if you are an enthusiast for new technology and having top computing performance is important for you, then of course SSD is the way to go.  Eventually SSD will replace HDD as the standard storage mechanism, certainly in laptops given the advantages they present for a mobile device. We are already seeing this happen with SSD showing up as the default storage device in the new Ultrabook category.  There will always be a market for both HDD and SSD, and the perfect solution may actually be a hybrid blend of both storage solutions. The advent of mSATA SSD devices and hybrid drives that include both SSD and HDD may be the best hope for reaching storage zen and giving you the best of both worlds, but that’s a topic for another day!

Curious about which SSD or hard drive to buy? Be sure to check out our constantly updated leaderboard that has a breakdown of the best SSD in categories like value, mainstream and enthusiast.

About The Author: Andrew Baxter is the Editor of LaptopReviews.com where he writes news and reviews covering the laptop industry. He is also a Contributing Editor at StorageReview.com.