The OcUK SSD- & Buyer's Guide: Everything You Need to Know about SSDs!
A Solid State Drive, or Solid State Disk (SSD), generally uses non-volatile flash memory nowadays. Non-volatile means that the data can be safely stored over the long term even without power being supplied. Memory, on the other hand, also uses flash memory – but in this case the data is stored only in so far as the memory cells are powered. In contrast to traditional hard drives (HDDs), SSDs contain no moving parts and thus produce no noise during operation as a result. Moreover, data on an SSD can be accessed at significantly faster speeds than on an HDD.
What to Factor in when Buying an SSDWhen buying an SSD, it’s usually sensible to take a few things into account first: form factors, data transfer protocols, interfaces, transfer rates, IOPS, TBW, and much more. Sound complicated? Don’t worry, we’re going to go in-depth and explore everything to do with flash storage below.
The Form Factor: 2.5” SATA SSD vs M.2 SSD vs PCIe-SSDThe question is, how do we decide on what form factor to choose when it comes to buying a new SSD? The answer to this depends on, among other things, both your current hardware as well as your intended upgrade path in the future. Factors to keep in mind include the space available in your case and the connectivity options provided by your motherboard.
Which SSD Should You Buy?Our online shop offers a wide range of SSDs with a variety of capacities. Of course, here at OcUK we have plenty of affordable SSDs to choose from, and if that isn’t your cup of tea then you might take a glance at some of our lightning-fast high-performance SSDs. Outside of SSDs primarily designed for use in gaming PCs, we also have a selection of enterprise class workstation SSDs.
Data Transfer Speeds: SATA6G vs NVMeThe speeds of SSDs are measured in terms of their maximum read- and write speeds, and the speeds achievable depend on the SSD’s connection with the motherboard. The physical connector used, whether that is PCIe, M.2 or SATA, is of little relevance to the data transfer rates. The decisive factors here are the protocol used and the internals of the connection. SSDs with SATA connections transfer data utilising the traditional AHCI protocol, while PCIe-based SSDs use the significantly faster NVMe protocol:
- SSD with AHCI / SATA port: approx. 600 MB/s (4.8 Gbit/s)
- SSD with AHCI / PCIe port: approx. 1000 MB/s (6 Gbit/s)
- SSD with NVMe / PCIe-Port (x4): approx. 4000 MB/s (32 Gbit/s)
SATA is short for Serial ATA (Serial Advanced Technology Attachment) and is an interface for transferring date to and from storage devices. Released in the year 2000, the roots of the Serial ATA standard lie in the older ATA standard. The third and most current revision, that of Serial ATA 6.0 Gbit/s (aka SATA6G, SATA III, SATA3, SATA-600) enables data to be transferred at speeds of up to 4.8 Gbit/s (600 Mbyte/s). The idea that any traditional HDD of the time achieving such speeds was rather optimistic. Even today, the SATA interface won’t break a sweat dealing with the speeds most HDDs are capable of. This is not the case for modern SSDs on the other hand, which bump up against the limits imposed by the interface with ease. In fact, SATA was never designed with fast flash-based memory in mind, and as such this venerable interface has more or less run its course at this point. The falling prices of fast SSDs have also played a role in reducing users’ reliance on this interface, even if HDDs still hold the crown in terms of raw cost to capacity – at least for the time being.
NVMe, also known as NVM Express stands for Non Volatile Memory Express and is a protocol that enables data to be carried over the PCI-Express interface. The SSD is connected either via an M.2- or PCIe slot. Having been designed especially with flash storage in mind, the NVMe protocol offers a marked increase in transfer speeds over the traditional AHCI protocol used in the older SATA standard. Designed originally for use in server- and other high-end systems, NVMe has begun to filter into the mainstream in recent years – with home users enjoying the benefits of shorter loading screens and boot times.
Data Transfer Protocols
The data transfer rate of an SSD consists of two values: the write and the read speed. The speed at which data can be stored on or retrieved from flash memory is measured in Megabytes per second.
A SATA SSD is limited by the AHCI protocol to just 600 MB/s. Modern SSDs with a SATA connection can usually saturate this interface. The average performance is upwards of 550 MB/s for read speeds and 500 MB/s for write speeds.
With a NVMe SSD on the other hand, users will achieve significantly higher speeds – as long as the interface supports them. The NVMe protocol unlocks data transfer rates of 1.000 MB/s per lane. PCIe- and M.2-SSDs, connected via 4 lanes, are thus capable of achieving speeds of up to 4.000 MB/s. NVMe SSDs for end users average speeds of around 2.000 MB/s in read speeds and 1.500 MB/s when writing. Top models reach values of 3.500 MB/s (read) and 3.300 MB/s (writes). Server-oriented high-end SSDs take things up yet another notch and deliver read speeds of up to 6.800 MB/s write speeds of 6.000 MB/s. Achieving these numbers requires the presence of 8 lanes as well as a PCIe-x8 slot.
Other Key Specifications of SSDs
Besides the interface and the resulting data transfer rate there are other values that help to define the overall performance of an SSD. With SATA SSDs, the performance values usually remain relatively close to one another. With NVMe-SSDs on the other hand, there can be large differences between individual models, depending on the connection type and the protocol used (see SATA6G vs NVMe).
The capacity of an SSD can vary between 120 GB, 240 GB, 500 GB, 1 TB, 2 TB and 4 TB. Depending on the model and manufacturer, there may also be some drives with capacities that lie in between these amounts. Some manufacturers also offer models with up to 30 TB capacity, although these are primarily utilised in the server sector. The capacity of some SSDs can also have a significant influence on their Read/Write speeds, meaning that the larger the drive the greater the speeds – although these differences are relatively marginal and would not necessarily be noticeable in day to day usage.
The memory chips of an SSD are subject to a certain amount of wear and tear. The flash memory can only withstand a certain number of storage cycles until it fails and no further data can be written to it. Manufacturers therefore specify a load limit or write load in TBW – standing for Terabytes Written or Total Bytes Written for their SSDs. This specification guarantees that the drive can endure a certain number of writes.
To give you a sense of proportion: an SSD with a TBW of 150 can endure 40 GB of data being written to the disk on a daily base for at least 10 years before the first cells cease to function. These are workloads that the average end user is very unlikely to subject their consumer SSD to, especially as this is merely a figure that defines that minimum number of possible writes as opposed to the maximum.
When it comes to PCIe SSDs it is also important to pay attention to the number of lanes used by the motherboard: Some boards, for example, only use two instead of four PCIe 3.0 Lanes or even the slower PCIe 2.0 standard to connect PCIe storage devices.
What not everybody may be aware of though, is the fact that a motherboard only has a certain number of data lines that can be used. The number of lanes available for use depends on both the processor as well as the motherboard. Most motherboards have more ports available than can, in fact, be used simultaneously. You can find all the information concerning any relevant limitations in your motherboard manufacturer’s instruction manual. One example might be that using an M.2 PCIe SSD can result in several SATA ports being unusable or that the PCIe lane allocation of a PCIe slot changes.
IOPS - Input/Output Operations Per Second – this can be broken down into two basic types, sequential and random. With sequential access, large amounts of data are transferred over a longer period of time. This presents no issues for modern SSDs and all SSDs will normally deliver good performance. In the case of random access, however, a lot of small data is being retrieved. This is far more demanding for the storage devices. There can be significant differences between SSDs from different manufacturers and models.
In simple terms, the higher the values, the better the SSD. In normal everyday operation, such extreme performance numbers are barely noticeable. They do however come into their own when the device is placed under heavy loads, as would happen in the server and enterprise sector.
How to Recognise an M.2 NVMe SSD or M.2 SATA SSDDepending on the application at hand, M.2 connectors are divided into Key-IDs. M.2-SSDs utilise M.2 Key M and/or Key B, while Key is often used for WiFi/BT modules, for example. M Key M.2 SSDs are connected via SATA and transfer data using the AHCI protocol. B+M Key M.2 SSDs can be connected via SATA as well as via PCIe are able to use both data transfer protocols.
- B Key: SATA SSD
- M Key: NVMe SSD
- B+M Key: SATA/NVMe SSD
There is only one small detail that gives the game away when it comes to identifying whether you have an M.2 SATA SSD or an M.2 NVMe SSD (M.2 PCIe SSD) on your hands: the connector. If it has a notch on the left side, it is an M Key M.2 SSD with PCIe connectivity. If, however, the connector is located on the right side, it is a B Key M.2 SSD with SATA connectivity. If the connector strip has two notches, it is a versatile B+M Key M.2 SSD.
Adapter CardsEven when it comes to older motherboards, just because they are no longer new, it does not necessarily mean that they don’t support fast NVMe SSDs in some form or another. These can be easily upgraded with a variety of adapter cards, as long as a PCIe slot is free. Click here for the adapter cards for M.2 SSDs in our shop: M.2 Adapter Cards.
SSD Cooling Solutions
Due to the high performance offered by M.2- and PCIe SSDs, they can become very warm when placed under heavy loads. In such cases, the SSD automatically throttles in order to avoid causing damage to the sensitive electronics. To prevent thermal throttling in this manner, PCIe SSDs usually come equipped with a pre-installed cooling system. With M.2 SSDs however this is relatively rare, which is why some manufacturers go to the trouble of offering heat sinks that are available for purchase separately.
The easiest way to kit out your M.2 SSD with cooling is to use passive air coolers. They are available from different manufacturers in a range of different sizes and designs. There are even heat sinks for integrating the drives into a water-cooled loop. Some motherboard manufacturers have belatedly recognised the need for additional NVMe SSD cooling, and we can see this in the manner in which ever more designs now include their own custom M.2 drive cooling solutions to help keep temps under control.
Check out the OcUK online shop to find the best affordable high-performance storage solutions for yourself: M.2 & SSD heatsink bundles.