How An SSD Works;formats, interfaces, characteristics

SSD absolutely dominates storage solutions for PCs , both those installed in new OEM equipment and in the retail market where it has become one of the best updates that a user can do to eliminate the bottleneck that for years they have course our dear, but today obsolete hard drives, relegated to other tasks such as external drives or NAS, as well as servers or data centers where they do have life ahead of them.

These solid state drives offer all the advantages of solutions based on NAND flash memories , mainly in terms of much higher performance when booting the operating system or applications, transferring files internally or to external drives, or recovering from data. systems from sleep modes.

Its advantages are also relevant in terms of consumption, heat emission or emitted noise , null due to the absence of moving parts of the mechanical units. In terms of robustness and resistance to failure, current SSDs equal or exceed hard drives in sections such as mean time between failures or in warranty, with five years in most mid-range series and above.

Finally, cite the possibilities of this type of drive in its M.2 format by offering a greatly reduced size compared to a hard disk, which allows leaving more free space on desktop PCs and especially laptops, an important section for slimmer and lighter designs.

SSD Technical Basics

Solid state drives serve the same purpose as a hard drive: to persistently store data and files . In this way and compared to other types of memory such as RAM, the data in an SSD is maintained even if we turn off the equipment. By saving data in non-volatile memories, they do not require any type of constant energy supply or batteries to avoid losing the stored data, even in the event of sudden PC blackouts.

How an SSD works

There is an important difference between the way an SSD handles data and how a hard drive does. An SSD writes data in chunks called “pages.” A group of pages is called a “block” and in order to write new data to a busy block, the entire block has to be erased first.

To avoid data loss, all information that exists in the block must first be moved to another location before the block can be erased. Once the data is moved and the block is erased, only then can it be written. This process is almost instantaneous but requires empty free space to work properly. If there is not enough free space, the process loses efficiency and slows down.

We comment on this technical section because it affects the capacity when we make the purchase of an SSD. To achieve maximum efficiency we should leave approximately 20 percent of the unit free . Hence, we recommend acquiring units with a capacity point more than what we really need. For example, the price of a 250GB model versus a 500GB model is usually not excessive and will be worth it.

Failure resistance

Another big difference compared to disks is that SSDs do not have moving parts, which gives them a great advantage in terms of the impossibility of mechanical failure. In contrast, SSDs are more prone to power failure while the drive is running, causing data corruption or even total device failure. Also, the memory blocks in an SSD have a limited number of write operations.

Fortunately, the last few years have vastly improved in reliability and massive endurance tests confirm that an SSD lasts longer than a hard drive before it starts to fail. In addition, all SSDs include free additional memory cells so that when the others fail, they do not lose capacity, reallocating bad sectors.

Types of memories

In the technical section, we must also mention the type of NAND flash memory used by these units. In recent times, manufacturers are betting on those that use QLC (quadruple cell level). This type of technology increases storage density and reduces costs, allowing models with greater capacity to be offered at lower prices.

The problem is that as the bits per cell increase , the resistance against previous formats such as TLC (triple cell level), MLC (double cell level) and especially SLC, Single-Layer Cell that only stores one bit per cell and that you will no longer see in the consumer market because they are not sold. All are already QLC and TLC. In any case, the best manufacturers have increased the guarantee up to 5 years in consumer units, while there are professional models with up to 10 years of guarantee.

Finally, we must point out the cache memory section because it has been controversial in recent months. Almost all solid state drives include additional memory for data caching. This type of memory is much faster than general NAND flash and allows to increase the performance of the unit, but only maintains its performance while its capacity lasts. The management of this cache memory is carried out by the installed driver and is internal, automatic and efficient. When it runs out, the aid runs out until it refills.

Always depending on the amount installed, a typical user does not usually notice loss of performance in common tasks. But it can be noticed in more advanced tasks or those that require moving a greater amount of data and that ends up depleting the cache. Some manufacturers are retiring this cache to reduce costs, but without the proper announcement. Be careful when purchasing because this cache is important for the performance of the unit.

Formats and interfaces on SSD

These units are marketed in various formats and standardized interfaces that every user should know when making their purchase for extensions or replacements of hard drives. We review them.

2.5 inches . It is a standardized format that is also used by smaller hard drives. It is the most widespread and versatile because you will find it in any desktop computer and almost in all laptops, whether they are new generation or older ones. In a PC tower you can mount any of these models in the 2.5 ″ bays and also in the 3.5 ″ bays with an adapter, while in laptops they vary according to their thickness of 9.5 mm and 7 mm the most thin and often used in ultraportables or convertibles.

M.2 . Much more modern and smaller in size than the previous one, it is marketed in several variants although the most widespread is the so-called ‘2280’ which measures only 80 x 22 and 3.5 mm, smaller than a RAM memory module. It is the format that is being imposed in the industry and the one recommended to use on motherboards that support it, both for size and performance when using the PCI-Express interface that we will see below. Another variant is mSATA, even smaller than the previous one (50.8mm x 29.85mm x 4.5mm), but less spread out.

Cards . A third format that we can find in this case exclusively for desktop computers is the card type inserted directly into a PCIe slot on the motherboard. This format includes the units that mount their chips directly on the card or if the card is used as accessories to be able to mount the previous M.2 cards on boards that do not have a specialized connector. They are just as fast as the M.2 when using PCIe, but they tend to be somewhat more expensive and their offer is much lower than the M.2 that are being imposed completely. We would really only recommend them when our board doesn’t have M.2 connectors available.

Related to the previous section, but very different, every buyer of these units must know the interfaces supported by their equipment or what is the same, the connection bus to which they are going to connect the SSDs. There are basically two:

SATA  ( Serial Advanced Technology Attachment ). It is a tremendously widespread bus since it has been with us since 2003 and is supported by 100% of the PCs sold in the last 15 years. Tremendously versatile, it is used only by 2.5-inch drives since the few M.2s that were marketed years ago for this port have practically disappeared.

Not all SSDs offer the same performance since they depend on the memories used and especially on their controller, but practically all SATAs exceed 500 MB / s, between double and triple that of a hard disk, although less fast than which we will see next. They are the cheapest SSD in cost per GB.

PCIe . More modern and much faster than SATA, PCI-Express has become the main local bus for PCs and the trend is that it will end up being the only one once all the existing legacy components for SATA are cornered. It is used both for internal connection in the integrated circuits of the motherboards (chipsets) and to connect external cards punctured in the corresponding slots.

In the case of SSDs, they have dedicated connectors on the motherboards, the mentioned M.2 and support the NVMe protocol that makes the unit bootable, allows to obtain a great performance, reduces the overload of the I / O components and the CPU. Among the few drawbacks compared to SATA models is that the PCIs get quite hot. Many manufacturers include heatsinks and the best motherboards do too.

The most popular drives connect to the PCIe 3.0 interface and offer speeds in environments of 3,000 MB / s in sequential reads, while version 4.0 raises the data transfer above 7,000 Mbytes per second. PCIe 5.0 is on the way, but there are no drives on the market yet.

M.2 PCIe and a SATA installed on the same board

SSD Offer (October 2021)

Solid state drives offer advantages in any type of equipment as we have seen and can be used in all types of computer equipment, laptops, tablets or desktops, either by replacing hard drives or together with them to maintain a greater storage capacity in an economic way . The combinations are varied and will depend on the needs and budget of each user.

The offer is very wide and any of the large manufacturers (Samsung, Kingston, OCZ-Toshiba, SanDisk-WD, Seagate, Intel) or the integrators that use the memories of the previous ones (Corsair, Crucial, ADATA …) sell varied interesting models in formats, performance, capacity and price. Since our last guide, the offer of PCIe drives has increased to the detriment of those that connect to SATA, although there is anything you are looking for.

We leave you with a representative selection of the available offer, separating it by the connection interface. We add a sample of external drives, another purchase option that has been gaining ground in recent years and that like internal drives offers multiple benefits over hard drives.


– Samsung 980 PRO . It has TLC memories and Elpis controller (both from the firm) and although it is not the fastest on the market, with 6,400 MB / s in reading – 2,700 MB / s in writing, it is one of the reference models in PCIe 4.0. It includes a large amount of cache (512 MB LPDDR4) and has a 5-year warranty. It is marketed from 250 GB to 2 TB, from 79 euros. Analysis here .

– WD_BLACK SN850 . It uses Kioxia (Toshiba) TLC 3D NAND memories, its own controller and is one of the fastest on the market by taking advantage of PCIe 4.0: 7,000 MB / s in reading – 5,100 MB / s in writing and up to a million IOPS in reading. With a five-year warranty and a very high TBW useful life, it is available from 500 GB for 111 euros, although the most attractive model in cost per GB is the 1TB for 184 euros. Analysis here .

– Corsair MP600 PRO XT . The newest on the list and surely the fastest: 7,100 MB / s and 6,800 MB / s in sequential reading and writing. It stands out in the cooling section since it mounts a spectacular memory sink as standard. It has a five-year warranty and lifetime resistance because the Tbytes written you will not be able to reach them in normal use. The 1 Tbyte version is priced at 200 euros and if you want more you have 2 and 4 Tbytes.

– Kingston KC2500 . One of the best PCIe 3.0 SSDs on the market with TLC memories, Silicon Motion controller and speeds of 3,500 / 2,900 Mbytes per second. Highlight the built-in hardware encryption with comprehensive data protection with 256-bit XTS-AES and the five-year warranty. It is available with capacities from 250 GB to 2 TB, from 50 euros. Analysis here .

– Crucial P5 Plus . More economical than the previous ones, it mounts memories of the house (Micron TLC) and offers speeds of 6,600 MB / s in sequential reads and remarkable speeds in writing: 5,000 MB / s. The 500 GB model is priced at 98 euros, although the most attractive currently by price is the 1 TB for 153 euros.

– Seagate FireCuda 520 . The other big one of the hard drives also packs a good solid storage offering. It offers maximum sequential read and write speeds of up to 5,000 MB / s and 4,400 MB / s, with capacities starting at 500 GB for 100 euros.


– Samsung SSD 870 EVO . Probably the best seller among the 2.5 ″ SATA. It mounts memories and its own controller and reaches the maximum performance that SATA allows with sequential speeds of 560/530 MB / s. It offers capacities from 250 GB to 4 Tbytes of capacity from 52 euros. The 1 TB intermediate version costs 109 euros.

– Crucial MX500 . In a 2.5 ″ form factor, it mounts Micron memories and offers sequential reads / writes up to 560/510 MB and random reads / writes up to 95/90 K. They have a 5-year warranty and offer capacities from 250 GB to 4 GB. Tbytes of capacity. Very cheap, they start at 44 euros and currently the most interesting in capacity / price is 1 Tbyte for 90 euros.

– Kingston SKC600B . Mounts Toshiba memory and Silicon Motion controller for 550/520 Mbytes per second in sequential read / write. It stands out for its compatibility with comprehensive security packages to safeguard data, XTS-AES compatible self-encryption based on 256-bit hardware, and TCG Opal 2.0 security management solutions. With a five-year warranty, it offers capacities from 256 GB to 2 TB with prices starting at 49 euros. Analysis here .

– SanDisk Plus . Another of the most representative of the 2.5 ″ SATA, it mounts its own memories for a performance of 535 MB / s in reading, although in writing it drops a little to 450 MB / s. Its price makes up for it since the 1 TB version costs 89 euros. It offers other capacities from 120 GB for 39 euros.

– KIOXIA Exceria . The new brand of what was previously Toshiba Memory, they mount memories of the house and transfer data of up to 555 Mbytes in sequential reading. The 1 Tbyte version is priced at 98 euros and offers other capacities such as 240 GB for only 31 euros.

– WD Blue . The world’s leading hard drive manufacturer also has an interesting SSD offering, like this model with sequential read speeds of up to 560MB / s and sequential write speeds of up to 530MB / s. The 1 TB model is priced at 99 euros and offers others up to 4 TB or the smallest, 250 GB for 39 euros.

External SSD

– WD My Passport Portable SSD . It supports the NVMe protocol to offer more than 1,000 Mbytes per second in read / write. It is offered in capacities of 500 GB, 1 TB and 2 TB, starting at 95 euros.

– Kingston XS2000 . New for the last month with a minimal size that can be carried anywhere in a pocket and connects to a USB Type-C port. IP55 certified for resistance to water, dust and shocks, it offers a very high performance with data transfer of 2,000 Mbytes per second in both sequential reading and writing. You have the 500 GB version for 97 euros.

– External SanDisk SSD . Small, robust and highly mobile. The company offers standard units at 520 Mbytes per second, the Extreme (1000 MB / s) and the Pro that offer 2,000 MB / sec, They offer all kinds of capacities and the base version of 1 Tbyte is priced at 118 euros.

– WD_BLACK P50 . Specially designed for gamers on consoles and PCs who need additional storage for their games. Its performance is very high up to 2,000 MB / s in sequential reading. It has an attractive and rugged casing and is sold in capacities from 500GB to 4Tbytes. The 1 TB version is priced at 218 euros.

– Seagate BarraCuda Fast SSD . All-purpose external SSD with a small footprint, attractive design and good performance connected to a USB Type-C port (540 – 500 Mbytes / sec). It is sold in capacities of 500 GB, 1 and 2 TB from 94 euros. (If you are interested,  we will analyze it here ).

– Samsung T7 . Small size, low weight, resistant and with speeds of 1,050 Mbytes per second. It is available in capacities of 500 GB, 1 and 2 Tbytes, with prices starting at 89 euros.


by Abdullah Sam
I’m a teacher, researcher and writer. I write about study subjects to improve the learning of college and university students. I write top Quality study notes Mostly, Tech, Games, Education, And Solutions/Tips and Tricks. I am a person who helps students to acquire knowledge, competence or virtue.

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