What type of SSD should I get?

You may be wondering what types of SSDs there are and what the features of SSD types are. In this guide, we will try to clear these doubts about SSDs and provide information about the types of SSDs available. Thus, you will learn the SSD types and features and understand the difference between them.

SSD (Solid State Disk) or solid state disk is a variant of the classic HDD. HDD consists of electromechanical parts and magnetic platters where data is stored magnetically, while SSD has no moving parts; there are only flash memory chips where data is stored electrically.

What are the types of SSD?

They can be classified according to their different characteristics. Therefore, the question of what types of SSDs exist is answered in several ways:

According to memory technology

One way to classify SSD drives is the memory technology they use. The main difference between them is the number of bits they can manage per cell or memory cell. We can find these basic types:

  • NOR: They use NOR gated flash cells, they were the oldest units and had a shorter lifespan.
  • NAND: These are the most modern and use this other logic gate which provides greater endurance and performance. On the other hand, depending on the type of NAND cell, some subvariables have been developed as follows:
    • SLC (Single Level Cell): It is an older type of NAND flash memory in which only one bit of information can be managed in each cell. However, its access is faster and more durable.
    • MLC (Multi-Level Cell): As the name suggests, it was also popular in some SSD drives and could manage two bits for each memory cell. This increases the storage density per cell, but also reduces the durability of the cells.
    • TLC (Triple Level Cell): performance is slightly lower and does not tolerate as many access cycles. The upside of this NAND flash cell is its larger storage capacity, so it has a good GB/€ ratio.
    • QLC (Quad Level Cell): This occurs as an evolution of TLC with the same advantages and disadvantages, but can store four bits instead of three.

SSD types by form factor

On the other hand, SSDs can be classified according to their form factor, that is, their physical properties and size. For example we can find:

  • 2.5″: Designed for use in laptops or desktops with bays of this size, which are smaller than the regular 3.5″ size that most HDDs usually come in. This format is the format used by SATA3 drives.
  • M.2: It is the most popular version that has become the current standard. It is a small module that plugs directly into a slot on the motherboard. This format also includes:
    • mSATA: It is a miniaturized format designed for equipment where size is more limited. They use SATA interface.
    • NVMe: They are smaller than their predecessors and have better performance when using the PCI Express interface.

SSD types by interface

Depending on the interface or connection, SSDs can also be classified as:

  • USB: SSDs generally do not have a USB connection, except for some external drives. However, internal SSD drives need to convert them to SATA/USB or PCIe/USB converter, etc. There are cases where it converts external drives using Speed is limited by the USB connector; For 2.0 to 5 Gb/s it is 480 Mb/s.
  • SATA3: This type of drive was initially popular, although it is still sold. They use a 2.5″ form factor and have a transfer rate of 6 Gb/s.
  • eSATA: a variant of the previous ones for external use. In this case, although the speed is 3 Gb/s, it shares the same features with SATA.
  • PCI Express: This interface is preferred by most SSDs considering their speed. It can transfer data at up to 15.8 Gb/s per lane of PCIe 4.0, 64 Gb/s per lane of future PCIe 6.0, and exceed 31.6 Gb/s per lane of PCIe 5.0.
  • NAS (Network Attached Storage): You can also find NAS units that use SSDs as main drives instead of HDDs. In this case, the interface is not wired (at least directly) as it connects to the network to access it remotely.

SSD types by drive

Depending on the SSD controller we can find two more different variants; one of them was mentioned above:

  • AHCI: Used in non-PCIe SSDs such as SATA.
  • NVMe: Used in most modern PCIe with better efficiency, performance and interoperability than their predecessors.

Internal or external

Of course, if we look at where SSDs will be installed, we can also distinguish:

  • Internal: for installation inside computers or cases and for permanent use.
  • External: for use as removable drives.