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Differences Between SSDs And HDDs - Characteristics And Types

The term hard disk has remained as a standard designation for storage units. Currently on the market we can find two large groups: SSDs and HDDs. SSDs are solid state hard drives or what is the same, they lack moving parts. While HDDs are mechanical hard drives or what is the same, they have mechanical moving parts.

The two types of hard disk differ not only by having or not moving parts, but also by their robustness, capacity, format, consumption, etc. We can also find different aspects that offer unique characteristics. For example, we can find SSDs SATA through this connector or through PCIe M.2.

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  • Sequential Write: 520MB / s
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What is an HDD?

They are storage units that have one or more mechanical parts. Internally they have mechanical plates where the data is stored and a moving head that reads the information. They are also characterized by being non-volatile memories, which means that the data is not erased when the computer is turned off.

The number of magnetic disks on a hard drive is what determines the final capacity of the drive. Currently, the data density per disk is also improved, which allows scaling in terms of storage capacity. The space between the discs has also been reduced through the use of special gases such as Helium, which reduces friction when rotating the discs.

HDD is the abbreviation in English for Hard Disk Drive

A moving magnetic head is used to read and write the data. Each disc has its own head. Currently manufacturers have separated the heads into double groups to avoid unnecessary wear on the part. And it is that the main reason for failure of a mechanical hard disk are the heads because they are mechanical parts.

A mechanical hard drive also has the problem of being very susceptible to shocks. Any impact can irreparably damage the drive and the data can only be obtained by taking a specialist in.

Toshiba N300 NAS HDD Hard Drive

What is an SSD?

They are solid state storage drives and are so named because they lack mechanical parts. They are manufactured based on an electronic circuit that integrates a controller, a DDR3-type cache memory and DRAM memory chips.

The controller is one of the most important elements of these units. It not only takes care of the input and output operations of the unit, but also takes care of the memories. Simply explained, the memories are divided into small data cells, something similar to a chessboard. What the controller does is prevent people from always writing to the same cell and distributes the load among all cells. If the unit has more than one memory chip, it spreads the load between the memory cells.

SSD is the abbreviation in English for Solid State Drive

On the other hand, we have the cache, usually made up of DDR3 memories. This type of memory is used because they are fast and very cheap. The function of the cache is to act as a data buffer to improve the performance of writing and reading the data.

SSD drives are being used more and more for computers and laptops, due to their increasingly affordable price. Although we will not go into depth, this is due to the type of memories used. Much progress has been made in this field and NAND Flash memories with a greater number of bits per cell and with a greater number of layers are increasingly being achieved. This allows to reduce costs and increase capacity.

kingston ssd now uv400 ssd

What is an SSHD?

You may not have heard of this type of unit and if you have it has been very in passing. SSHDs or hybrid state hard drives are quite rare to see today. They were launched shortly after the arrival of SSDs to improve the performance of mechanical hard drives. And it is that initially the SSD have astronomical prices and low capacities, something that is far from the present

SSHD is the abbreviation in English for Solid-State Hybrid Drive

A small amount of SSD memory was installed in the HDDs that served as a cache. It allows to improve the transfer speeds of mechanical hard drives a bit, although it was not too much.

They never finished curdling in the market since the performance improvement was little compared to the price. With the fall in the price of SSDs they have ceased to have value for the market, therefore, they have ended up disappearing. They can still be found, but they are quite rare and their benefits do not compensate.

Formats of mechanical hard drives (HDD)

Because they have moving parts, there are only two formats in which we can find an HDD: 2.5-inch format and 3.5-inch format. It should be noted that these are two standardized formats to avoid incompatibility problems and facilitate the construction of systems.

We have to emphasize that the current HDDs that are sold for the domestic sector works through a SATA connection. Although there are other types of connection formats, they are not interesting for the average user, they are intended for professional environments.

Format 2.5 inches

This format is typically reserved for extremely compact laptops and systems. It is not a format at all intended for desktop computers, although it could be used without problems.

Most HDDs of this format are intended for simple systems and are characterized by low working speeds. 2.5-inch HDDs mostly work at 5400RPM, although there are 7200RPM, but they are the least. This is because space is very little and working at such high speeds significantly increases wear.

RPM are the revolutions per minute that the discs of these units make.

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Format 3.5 inches

Possibly the most common format today. Here the range of disc speeds is wider. The energy efficient units are characterized by operating at speeds of 5400 RPM. The 'normal' and more common drives operate at 7400 RPM. Finally we can find high performance drives at 10000 RPM.

Of course, the higher the speed of rotation of the discs, the greater the wear on the unit. There are even 3.5 inch HDD drives that work at higher speeds, but it does not seem relevant to us either since they are intended for professional environments.

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Solid State Hard Drive (SSD) Formats

There is a lot more variety here because these units are characterized by being completely electronic. By lacking moving parts, it can be integrated into more formats that improve the performance of the unit.

Format 2.5 inches

For many years it has been the standard format in the industry. Initially, some large-capacity models were seen in the 3.5-inch format, but they have been relegated to the professional segment. The 2.5-inch format is standardized for both desktop and laptop computers.

The great advantage that this format offers us is a solid and compact construction that allows the unit to be cooled. As a major drawback we have that it is based on the SATA connection, slower than other formats.

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  • Improved Bug Fixes
  • Support for gifted wipe, safe, disk cloning, FW update and much more.

M.2 SATA format

They are the compact version of the 2.5-inch drives and integrate directly into the M.2 ports on the motherboards. They offer roughly the same read and write speeds as 2.5-inch drives because they are also based on the SATA interface.

Visually these units can be distinguished because they have two notches on the connector.

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M.2 PCIe format

Eerily, this format is commonly referred to as M.2 NVMe, referring to the type of memory. What these types of drives offer us are based on the PCIe interface, which offers higher read and write speeds than the SATA interface.

Visually these units can be distinguished because in the connector they only have a notch.

Samsung 970 EVO Plus MZ-V7S500BW, Internal NVMe M.2 SSD, 500 GB, Up to 3,500 MB/s sequential read
  • SSD with V-Nand Samsung technology. Power Consumption (Standby): Max. 30mW Actual power consumption may vary depending on system hardware and configuration > Operating temperature: 0 - 70℃
  • The 2,5-inch format is ideal for desktop laptops. Encryption support: AES 256-bit encryption (class 0) TCG/Opal IEEE1667 (encrypted drive)
  • SATA 6 Gb/s interface and backward compatible with SATA 3 Gbps and SATA 1,5 Gbps
  • Sequential read speed up to 3500MB/sec and sequential write speed up to 3300MB/sec
  • Random read (4KB, qd32) and up to 600000 IOPS, random write (4KB, qd32) up to 550000 IOPS

PCIe format

For the consumer sector there is yet another format, such as the PCIe format. These drives are characterized by plugging directly into a PCIe port on the motherboard. These are usually PCIe x4, although some drives can become PCIe x16.

Within this category we can even find two aspects. The first are the units that already integrate the NAND Flash chips on the PCB or those that allow connect M.2 drives. It should be noted that this second format is normally used for RAID configurations that allow combining several units into one or making automated backups.

Corsair Neutron NX500 - Solid State Drive, 400 GB SSD, PCIe 3 x4 NVMe-SSD, Read Speed ​​up to 1.600 MB / s
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  • Ultra-efficient cooling - The heatsink is specifically designed to keep games running at peak performance
  • Multi-level cell endurance - Improved reliability and performance over triple-level cell (TLC) SSDs

On board integration

Some laptop manufacturers are starting to choose to directly integrate the chips into the laptop motherboard. It is something perfectly plausible and simple to do and that reduces even more space, allowing to make even more compact notebooks. Apple was one of the first manufacturers to make this decision.

Perhaps the negative part is that the extension by the user is impossible and the repair becomes more difficult.


Differences between HDDs and SSDs

We are going to see the big differences between solid state hard drives and mechanical ones. Let's compare the 3.5RPM 7200-inch HDDs with the 2.5-inch SSDs, the M.2 PCIe and the PCIe ones. We do this because 5400 RPM HDDs are not typical for desktop. The M.2 SATA only in the best of cases can offer 10% more speed than the 2.5-inch SSD. We believe it is more interesting to see the most common formats.


Although HDDs offer higher capacities for lower prices, the gap has narrowed a lot. SSDs are already starting to offer 1TB of capacity below € 100, a really sweet price for users. This makes the HDD go into the background, being units for massive data storage.

Users are usually recommended to go for a 256GB or 512GB SSD and a mechanical hard drive for game installation and data storage. Although with capacities of 512GB we could even forget about the HDD, since it is more than enough capacity to install games.

HDD capacities range from 512GB (although rare and 1TB is the norm) to 14TB for the professional sector. For the domestic sector, the most common are 1TB and 2TB, although there are also 4GB, 6GB and 8GB.

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On the other hand, in terms of the SSD there are them of different capacities. SATA usually go from 120GB (not recommended) to 4TB, the latter being very expensive. 256GB, 512GB and 1TB capacities are the most common and the best priced.

The M.2 format in its PCIe aspect and in its SATA aspect are limited to 2TB in the 2280 standard (80 indicates the length of the PCB) due to the capacity of the memories. The normal thing is the units between 256GB and 1TB.

Finally, the PCIe format is more expensive and offers more or less the same capabilities as a SATA SSD. The problem with these units is the type of interface they use, which requires better controllers and other elements. Perhaps the least interesting today and therefore the least in demand.

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HDD fragmentation

The rotating recording surfaces of mechanical hard drives work best with large files recorded in solid blocks. This is because the reading head must travel very little to read all the data. Hard drives do not normally handle this and spread the data over the entire surface of the drive, generating fragmentation. This makes the head have to move and reduces the speed of reading and writing, in addition to reducing the useful life.

Here solid state hard drives have no problems, since where the data is it does not matter. They are accessed electronically and this allows it not to affect in the least, only needing to know the memory address where the information is stored. This makes them highly efficient and fast units.

Never perform a defragmentation to an SSD, since we can damage the unit or significantly reduce its useful life.

hdd fragmentation

Loudness of SSD and HDD

As we have said, HDDs have mechanical parts that generate noise and vibration. Depending on the speed of rotation and the amount of work to be done, this may be higher or lower. SSDs have the advantage of not generating the slightest noise as they are completely electronic. This is one of the strengths of SSDs.

hard drive hdd

SSD and HDD dimensions

Mechanical hard drives, as they are based on turntables and have a moving head, have limitations in terms of dimensions. It is physically impossible to go beyond the 2.5-inch form factor and it offers even worse performance than 3.5-inch drives.

We have seen that SSDs have multiple formats, among others, because they lack moving parts that limit them. As they are based on memory chips, they can be installed on PCBs of different formats. As we have said, they can even be installed directly on the motherboard, as in some laptops, something impossible for an HDD.

Consumption of SSD and HDD

This is another differential factor that greatly benefits SSDs. An HDD does need 12V for the motor and the moving parts, which generates a high consumption. Depending on the unit, it can go from 20W to 50W. While the SSDs are electronic and work between 1.2-1.5V, having a maximum load consumption of up to 5W.

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SSD and HDD temperature

Normal HDDs and SSDs do not have temperature problems, although more modern M.2 PCIe do. This is the biggest problem with drives that are based on PCIe 3.0 and PCIe 4.0, the temperature. They require heatsinks to manage heat, since if the critical temperature is reached, performance plummets.

This phenomenon is called Thermal Throttling and causes the unit to degrade its performance to avoid damage.

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  • Total capacity: 2000 gb
  • Sequential read speed: up to 5000mb / s
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Durability of SSD and HDD

We move on to perhaps one of the most complicated factors to quantify and which depend, above all, on use. The lifespan of hard drives is typically measured in times the drive fills, especially for SSDs. Especially where they suffer the most is the process of erasure and rewriting.

HDDs, having moving and mechanical parts, have a useful life limited to the number of read and write cycles. In order not to complicate it too much, the most common for an average user is between 5-7 years. If it did not have these moving parts its useful life would be practically infinite based on magnetism.

On the other hand, SSDs do have a useful life, since they are based on NAND gates that have a number of operating cycles. But it is that this useful life also depends on the amount of bits stored per cell. Normally, under normal conditions and to simplify it enough, the useful life is estimated to be 10-12 years.

Read and write speed of SSD and HDD

Here is the key factor. HDDs are not limited by the connection interface, they are limited by being mechanical. This is the great advantage of SSDs, which, being electronic, can greatly squeeze the speeds of the connection interface.

Theoretical ReadingTheoretical WritingCommercial ReadingCommercial Deed
HDD 7200RPM400MB / s 350MB / s 150-120MB / s 80-150MB / s
SSD SATA600MB / s600MB / s400-550MB / s350-500MB / s
M.2 SATA600MB / s 600MB / s 400-550MB / s 370-520MB / s
M.2 PCIe 3.03950MB / s3950MB / s 3000MB / s 2500MB / s
M.2 PCIe 4.07880MB / s7880MB / s 5000MB / s4950MB / s

Note: The commercial values ​​are an approximation and always depend on the manufacturers


There are different factors to take into account when deciding on an HDD or an SSD. If we seek to obtain the best performance, greater reliability and greater durability, SSDs clearly win. In contrast, if what we are looking for is massive storage, HDDs offer us a great advantage, as they are cheaper.

The biggest and only advantage of HDDs is the cost per GB, much lower than in the case of SSDs. Solid state hard drives are better for the rest of the features. Perhaps the most negative element of SSDs is that M.2 PCIe drives require a heatsink to avoid temperature problems.

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Robert Sole

Director of Contents and Writing of this same website, technician in renewable energy generation systems and low voltage electrical technician. I work in front of a PC, in my free time I am in front of a PC and when I leave the house I am glued to the screen of my smartphone. Every morning when I wake up I walk across the Stargate to make some coffee and start watching YouTube videos. I once saw a dragon ... or was it a Dragonite?

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