With Solid State Drives becoming more prevalent in computers, I am frequently hearing the question; “What’s the difference between HDDs and SSDs, which is better or why should I care.” Understanding the difference between the two can help you to better understanding your technical support’s jargon and help to make important decisions if and when a device is struggling and if a simple part replacement can alleviate your performance issues. The following article will cover the significant differences between a HDD and a SSD.

What is a HDD:

HDD: is an acronym for Hard Disk Drive (HDD for short), they have been around for over 50 years and they continue to increase in capacity while decreasing form factor (size)hard drive

How do HDD’s work:

If you ever got curious, opened up and looked inside a HDD, you would see it consists of one or more circular platters, an actuator arm with a read/write head on it for each platter and a motor to spin the platters and move the arms. In addition there is also an I/O controller that communicates with the system and controls what the hardware does.

What are some benefits of HDD:

Some benefits of a hard disk drive is that it has been around for a while and is a proven technology. It is generally less expensive than its SSD counterpart with the same amount of storage. HDDs also have more storage space than SSDs but SSD are catching up.

So we now have some good information about Hard Disk Drives, let’s briefly talk about SSDs.

What it a SSD

SSD: is an acronym for Solid State Drive (SSD for short), its technology has been around since the late 70s but did not start seeing a rise in commercial popularity until the late 2000 making it a younger technology in comparison to its HDD counterpart.ssd drive

How do SSD’s work: 

In layman’s terms you can think of an SSD as a large USB flash drive; they use the same base technology. The technology in solid state drives, is a kind of flash memory called NAND Flash, (its a term for the silicon chips that comprise the actual storage on the SSD) It stores and retrieves data using only electronic circuits without any involvement of moving mechanical parts. Because it has no moving parts it is much faster than traditional HDDs.

SSD technology is a complex topic, so we’ll not go in depth here, if you are interested you can read more about it here.               

What are some benefits of SSD:

The key benefit to Solid state drives is they are much faster providing faster load times for applications and operating systems. They are also lighter and because they have no moving parts, they are better able to withstand being dropped, significant movement will not hinder them and they are completely silent. On top of all of this they are run cooler and use less energy.

Now that we know a little bit about the two, let’s compare them:


SSD: Have significant read/write speeds, upwards of 2,700MB/s (2.6GB/S). The high Input/output Operations Per Second (IOPS) wins the speed test for the SSD. As we mentioned previously, it has no moving parts so it does not have the physical seek limitation that HDDs have.

HDD: Have spinning platters that rotate from 5400 RPM up to 15000 RPM, they have a read/write head that positions its self over the spinning platters to read or write data.  When discs begin to fill with data the heads must access multiple sections of the disk – an operation called fragmenting. SSDs are not subject to fragmenting because read/write operations access cells simultaneously. This makes SSDs much faster than HDDs.


SSD: In its earlier life there were concerns with life expectancy compared to that of the HDD as a SSD lifespan has a built-in “time of death”. Data can only be written on a storage cell inside the SSD a finite number of times before it fails, the cells degrade with every write onto the SSD (between 3,000 and 100,000 times during its lifetime). To compensate for this, algorithms were developed and implemented to distribute data over all the cells evenly by a controller, thus expanding its life. You can check the status of an SSD by using a S.M.A.R.T. analysis tool, which shows the remaining life span of an SSD.

HDD: Do not have this finite write concern like the SSD, If not for the mechanical failure of its moving parts it could last indefinitely, this is not the case however. An HDD relies on moving parts for the drive to function. In fact a HDD has many moving parts and it would only take one of them to fail to render the drive unusable. HDD are also more susceptible to falling damage because of these moving parts.  

Storage capacity:

SSD: Has slowly been notching its way up the latter with regards to storage and is now over taking HDD in capacity limits. The average SSD on the market currently is between 500GB to 4TB averaging at a price point of about less than $.10/GB. Though SSDs with capacities reaching 50 and 100 Terabytes are now being released, they come with a significant price tag of around $400/TB and are not for the average consumer.

HDD: Has been the primary technology when it comes to storage capacity for a long time. HDD deliver tons of storage at a low prices. Average drive capacities available for HDD is 1-12 TB. With the largest one found on the market today at 18-20 TB. If you are looking for large quantities of storage without concerns for speed, HDD is a good choice with an average cost around $.01-.02/GB.


SSD: Has no moving parts thus they are not subject to making noise. A properly secured SSD would literally make no sound.

HDD: Have components that move, read arms that click, and platters that spin, the faster the RPM of the HDD the more noise it tends to make. When drives begin to die they tend to make more noticeable whining, grinding and clicking sounds.  

Form Factor:

SSD: Can come in all shapes and sizes and continue to get smaller. You can purchase SSDs in the standard 2.5 in sizes to allow them to comfortably fit in the standard drive bays. Other form factors are becoming increasingly popular such as the M.2 (See below) which have a variety of lengths ranging from 42mm up to 120mm.

HDD: Because hard drives rely on spinning platters, there design is more limited. Increased capacity requires increased number of platters, which require increased number of read/write heads. Because of this they can only shrink so far.

SSD interfaces:

Let’s discuss briefly the different interfaces SSD commonly use.

Serial AT Attachment (SATA): is a computer bus interface that connects the SSD to its host and is currently the dominant interface in most computers. It is also the slowest, though most common tasks will not notice this. Over the years there have been releases of several revisions, the latest generation, SATA revision 3.0 has a transfer rate of up to 6 Gb/s.

Serial Attached SCSI (SAS): is primarily used with enterprise solutions and offers optional compatibility with Serial ATA (SATA). This allows the connection of SATA drives to most SAS, however the reverse, connecting SAS drives to SATA, is not possible. SAS-1 was introduced in 2004, there have been several iteration since then with the latest SAS-4 release having transfer rates up to 22.5 Gbit/s. (SAS-5 is in development with expected transfers up to 45 Gbit/s.

PCI Express (PCIe): Peripheral Component Interconnect Express, It is the common motherboard interface for personal computers and hardware connections such as video cards, WiFi adapters, etc. It too has been around since the early 2000s, and has had its share of revisions and improvements. 

“Non-Volatile Memory Express” (NVMe), is a logical-device interface layered over top of PCIe, it is designed for accessing solid-state drives via the PCI Express (PCIe). NVMe can deliver transfer rates much higher than the previously mentioned SATA/SAS.

A recap of HDD vs SDD difference:


  • Have been around longer is a long known proven technology.
  • Use spinning platters and re/write heads to store data.
  • Lower in cost per GB.
  • Are slower.
  • Louder
  • Limited form factor

  • Stores its data on silicon chips.
  • Have no moving parts.
  • Costs more per-GB.
  • Are faster than HDDs.
  • Literally no sound.
  • Increasing in popularity
  • Greater variety of form factors.
  • Greater transfer speeds

Over the years storage has grown, advanced, and taken on new forms. Yet the question still stands, which is the better choice? In the end, each scenario and situation is different from each other and no one answer is the correct one. HDD will be around for years to come, but history shows that SSD advancements will lead them to be the dominant choice in the near future. Should you decide to upgrade your HDD to SSD here's the article on how to do it yourself.

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