How to choose an SSD on a flash sale
Which SSD to buy? Normally, we’ll just tell you to follow our guide to the best storage. But during flash sales, like on Black Friday or during the holidays, recommendations based on normal prices become somewhat irrelevant since the best deals often go to lesser-known players (models, capacities, etc.), which may worth buying at a good price. reduction.
In this scenario, you may be faced with several questions such as … is QLC as good as TLC? Do SSDs Really Need DRAM? Why do SSDs have different shapes? Does SSD capacity affect its performance? This short guide will walk you through the basic differences between all types of consumer SSDs. So when you see an SSD for sale, you’ll know if it’s a good buy for you.
NVMe vs SATA SSD
The SSD interface not only determines the transfer speeds, but also whether you will be able to install it in your system. For years, SSDs used the same SATA interface as hard drives and were either similar in shape / shape to the 2.5 “drives used in laptops; or they used the more compact mSATA form factor, which was similar to the Mini PCIe used by devices such as network cards.
With SATA 3.0 becoming a limit on transfer speeds to around 560MB / s, the NVMe interface effectively replaces it, connecting directly to the processor or through the motherboard chipset with multiple PCIe lanes, for much faster speeds.
Many motherboards have more connectors than they can use at the same time, so regardless of your choice of SATA or PCIe, you should check to see if using a connector in this mode would disable another one you want to use. you need.
The Crucial MX500 is about as good as a SATA drive can get. If you want an NVMe drive, the Western Digital Black SN_750 currently offers great value for money.
Expansion card vs M.2 SSD
Most current SSDs, SATA and NVMe, use the M.2 form factor, which supports up to four PCIe lanes for an NVMe SSD.
With M.2, PCIe 3.0 SSDs provide transfer speeds of up to 3,500MB / s, while PCIe 4.0 SSDs enjoy speeds of up to 7,000MB / s, as long as your CPU and card are used. mother support faster 4th generation interface.
Most M.2 SSDs are notched to the M key, which supports up to four PCIe and SATA lanes. Some older motherboards have M.2 slots that support Key B and only two PCIe lanes in addition to SATA.
Most SSDs that use SATA or two PCIe lanes are double-notched according to the two keys for compatibility, however …
All M.2 SSDs are 22mm wide. The most common are 80mm long and are called “2280”. Laptops, and especially ultrabooks, sometimes only have room for 42mm long SSDs, called “2242s. Tablets such as the Surface Pro 8 use 30mm long SSDs (” 2230 ” ). 60mm long (“2260”) SSDs are widely supported, but not common. The few that are 110mm long (“22110”) are not supported by consumer devices.
As an alternative to M.2, some PCIe SSDs come in the form of expansion cards, looking like small graphics cards and installed the same way. The larger form factor can compensate for a motherboard’s lack of PCIe 4.0 support by using eight PCIe 3.0 lanes, or accommodate a more powerful controller that requires better cooling. Another alternative is a 2.5 ”U.2 SSD which can be connected to an M.2 slot with an adapter cable.
Western Digital’s AN1500 is probably the fastest SSD when connected to a motherboard or PCIe 3.0 processor only. If your system supports PCIe 4.0, the Samsung 980 Pro is a first choice.
QLC SSD vs. TLC
In modern SSDs, flash chip cells are made up of levels, with each level storing one bit (0 or 1) of data. Most SSDs today use either three-level cells (TLC) or four-level cells (QLC). The term “multilevel cells” (MLC) was originally used to describe two-level cells, but the term “3-level MLC” used by Samsung simply means TLC.
Adding levels to cells allows them to store exponentially more data in the same physical space, but also makes them exponentially slower to write. The good news is, you won’t notice it immediately thanks to the clever caching mechanisms.
Most SSDs use part of their free storage space as Single Level Virtual Cell Cache (SLC) by writing only to the first level of cells. After the cache is exhausted, the drive degrades to its “native” write speed. In the case of QLC, this speed can be similar to that of a hard drive.
Whether it has QLC or TLC, the less free space your SSD has, the smaller its SLC cache will be and the shorter the time it will be able to maintain its maximum write speed.
If you really need an 8TB SSD, the Sabrent Rocket Q is the best choice for you. If you can get by with 4TB or less, the company’s Rocket 4 Plus will perform more consistently thanks to its TLC flash.
DRAM-free SSD or DRAM-equipped SSD
In order to map where each file’s data is physically stored in the flash chips, most SSDs rely on their own local RAM – usually 1MB of RAM for every GB of storage space – but that’s not still the case.
NVMe SSDs often use the host memory buffer (HMB) to use part of the system RAM for the task. In shorter M.2 SSDs, this can be done in order to save physical space. In larger SSDs, the goal is to reduce costs.
When a drive that uses HMB is nearly empty, the lack of onboard DRAM will not significantly affect its performance. However, if you store hundreds of GB of data in it, the speed at which it finds files can become several times slower (but still much faster than a hard drive).
With SATA SSDs, things are more complex. Instead of the main system RAM, DRAM-free SATA SSDs use their own flash chips, which are much slower than any type of RAM. Additionally, storing the ever-changing index of all your data on flash chips can accelerate their wear and tear and adversely affect the lifespan of the device. For this reason, we can only recommend a DRAM-free SATA SSD as a temporary solution.
If you are looking for a short NVMe drive, then the DRAM-free Rocket Nano from Sabrent is your best choice. Instead of buying a DRAM-free SATA drive, you should look for something like the Western Digital Blue SSD (2018), which is never far from the best SATA drives, and often cheaper on sale.
250 GB versus 500 GB SSD
Over the past year, the demand for low-cost PCs for working from home has made 250GB SSDs almost as expensive as their 500GB versions. In a flash sale, however, a 250GB SSD can suddenly cost the same price per GB as a similar drive with double the capacity. The question is whether the 250 GB drive will be good value for money in this situation?
This may not be the case for two reasons: 1) Even though they use the same percentage of their free space as SLC cache as larger capacity disks, smaller disks still have smaller SLC caches to begin with. 2) Because they use fewer flash chips, they may not take full advantage of a controller designed to write to multiple chips simultaneously.
In NVMe drives, you might notice this immediately: for example, the 250 GB version of the Samsung 980 (not Pro) is designed for a maximum write speed of 1300 MB / s, while the 500 GB version is designed for double that speed.
In SATA drives, you might not see the difference until the SLC cache is full. The Crucial MX500 250GB and 500GB versions both start long writes at around 450MB / s, but when their SLC caches are full, the 250GB version drops to 200MB / s, while the 500GB version stays at a respectable 400MB / s.
If you want a good, affordable 500GB SSD, consider the Samsung 980 (non Pro). Instead of buying the 250GB version, you should look to the 500GB version of Western Digital’s Blue SN550 for a similar price.