How to choose an SSD for your PC or laptop

SSDs have gone from being an expensive, low-capacity storage device to a widely available consumer solution in recent years, and while SSDs are still more expensive per gigabyte than hard drives, many people are turning to SSDs for At least one system installation. However, it makes sense to wonder how to get lost in the variety of SSD drives, and how to choose the best one. We will talk about that in this article.

SSD form factor

The first thing to decide is the type of SSD connection. In the case of cheap and/or old laptops, there are unfortunately not many options: if there is a hard drive, you can always replace it with a 2.5″ SSD with a SATA interface connector. Alternatively, if a laptop has a disk drive, it can be replaced with a socket with a SATA interface inside (the whole design is called an Optibay) – this will not remove the hard drive, meaning there will be two drives in the system .

In the case of the most recent laptops and some PCs, it is possible to put an M.2 SSD. Unlike 2.5″ SSDs, which only connect via SATA, M.2s can also connect via PCI-Express. PCI-E compatibility makes sense: SATA3 has a maximum bandwidth of 500-600 MB/s, more than enough for hard drives, but some SSDs can run at higher speeds, which PCI-E provides. In the case of M.2, there are two options:

  • PCI-E 2.0 x2, with a bandwidth of 8GB/s, which gives a speed of about 800MB/s in practice;
  • PCI-E 3.0 x4, with a bandwidth of 32 Gb/s that gives a speed of about 3 GB/s in practice.

    • You can find out which option is implemented on your motherboard on the manufacturer’s website; you have to look at the type of key, there are only two: there can be a B key and an M key. If the motherboard has a B key connector, then the first option is implemented with PCI-E 2.0, respectively if the key M, so the second option with PCI-E 3.0. Both connectors support the connection of an M.2 SSD with SATA interface (these SSDs have a notch for both keys, i.e. M+B):

    Consequently, PCI-E SSDs with key B and M look like this

    As you can see in the photo above, PCI-E SSDs with different keys are not physically compatible, that is, you can’t put the SSD in a slot that it doesn’t support.

    The variety of M.2 SSD drives does not end there: they can also come in different sizes. There are three variants in total: 2242, 2260 and 2280. The first two digits are the same for all: it is the width of the SSD. The second two numbers are the length. A smaller SSD can be installed instead of a larger one: so for example, if your motherboard has room for 2280, 2242 will fit just fine. But if the board only has room for the 2242, the 2260 won’t fit because other items on the board will interfere with it.

    And finishing off the form factors is the SSD, which will plug into the most common PCI-Express expansion slot found on almost any PC motherboard:

    Typically these SSDs are PCI-E M.2, simply plugged into an adapter plate, so speeds here are the same as with M.2.

    Types of flash memory in SSDs

    The main difference between the memory chips of the different SSDs is the number of bits that each memory cell can store. There are three types of cells in total:

    NAND feature

    SLC

    MLC

    FTA

    bits in a cell

    1

    2

    3

    overwrite cycles

    100000

    3000

    1000

    Reading time, ns

    25

    fifty

    75

    Programming time, ns

    ~250

    ~750

    ~1000

    Erase time, ns

    1.5

    3

    4.5

    As you can see, SLC (Single-Level Cell) drives are the fastest and most reliable, but a cell only contains 1 bit of information, so the capacity of such drives does not exceed 64 GB. Also, SLC memory is the most expensive, and for the price you’ll have to pay for a 64GB SLC SSD, you can get a 500GB MLC SSD. Since the reliability of SLC for consumer use is excessive, there are hardly any SSDs with SLC memory on the market, and there is no reason to buy them in a typical PC or laptop.

    SSDs with MLC cells (Multi-Level Cell, although by “many” here we only mean two) have much lower reliability and slightly higher latency, but already allow 2 bits per cell to be written. The price per gigabyte of these SSDs has been rising steadily, and there is a full range of capacities on the market, from 8GB to 2TB. These SSDs are well suited for high performance PCs and laptops where speed and robustness are essential (3,000 write cycles on a 100GB SSD will write 300TB of data – it will take a year to download that! amount of Internet at 10 MB/s!)

    TLC (Triple Level Cell) – These are the older cells, first used in flash drives and later moved to SSD drives. They only have 1000 rewrite cycles and have relatively high latency, but they can write 3 bits per cell and are relatively cheap. These SSDs make sense for simple laptops and PCs where there’s not a lot of load on the drive and speed isn’t important – the bottom line is that these SSDs will still be considerably faster than the best hard drives.

    There are also Intel Optane SSDs with the new 3D-Xpoint memory, but for now they are only sold as cache to speed up a system with a hard drive, which will be worse in speed than installing the system on a full SSD. Considering that this type of SSD cache is also very expensive (starting at $70 for 16GB) and that they are only compatible with systems with Intel Kaby Lake (7th generation Intel Core processors), it doesn’t make sense to buy them at the moment. .

    SSD Controllers

    Controllers are the “brains” of SSDs, they have to process the information they receive and put (or retrieve) it into memory quickly. And if the controller is slow, an SSD with even the best SLC memory will run at the speed of regular flash drives. There are quite a few controller manufacturers on the market, let’s see the main ones:

    • SandForce – The controller has no “external” cache, is multi-threaded read/write capable, and has the fastest (claimed!) read and write speeds to date. Performance on random and sequential linear read/write tests drops by almost a third in busy zones and is no longer recoverable after data wipe.
    • Marvell – one of the fastest and relatively cheap drivers based on usage statistics, it is “immune” to the degree of data compression, and overall drive speed drops slightly over time.
    • Intel – A driver that has proven itself in server applications, where Intel has traditionally excelled. Not bad in workstation scenarios either. The downside is the slow write speed, which is practically invisible for everyday tasks.
    • JMicron – First generation SSD controllers, not well suited for flash memory, poor performance, and only 16KB cache (causing it to overflow when drive load increases and the system hangs for one or two minutes while waiting for the buffer to clear). The only advantage of drives based on this controller is their relatively low price.
    • indilinx – A controller adapted to SSDs that has no Jmicron drawbacks. Its main feature is excellent writing performance. The balanced performance (nearly equal read and write speeds) allows us to recommend drives based on this driver for large files. Cleaning support is present, but works less efficiently than with Intel. Performance is highly dependent on the size of the drive.
    • samsung – A Korean driver designed with JMicron’s shortcomings in mind. Despite the large cache size, there is no decent alternative to Indilinx. System no longer hangs, sequential read/write performance is on par with Indilinx and sometimes even higher, but the problem is non-sequential write, which is not high speed. The 850 EVO and PRO series have solved the problems of slow non-sequential write speeds, so their controller is one of the best.

    laptop, pc, ssd