Hello guys,
I'm sure that most of you already know about Solid-State Srives (SSD), but you might not know all the ins and outs of the different characteristics and types of SSD. There are actually a lot of different variations that are significant and you should know about it for the next time that you go and buy one otherwise, you might not get the maximum speed that each one is capable of, and you might waste money on something you don't need or you might just get something that is completely overkill.
[1]I'm explaining everything from different protocols to connectors, shapes and hopefully by the end, you should better understand it.
The first characteristic I’m gonna go over is the “Physical Interface” basically, the physical method of the connection between the SSD and the rest of the computer. A couple examples I’m gonna expound on are “SATA” and “PCI Express”. You may have heard of these but I do want to make a distinction, when I'm talking about the physical interface, I'm not referring necessarily to the connector but rather, the method that is used.
For example with SATA, there are different types of connectors, the internal connectors and the eSATA external connectors and they both use SATA but they just look different.
[2]
SATA and eSATA
[3]
PCI Express
The same idea is with PCI Express, you have different slots that are different sizes but they still use PCI Express. Just keep that distinction in mind that the SATA or PCI Express interfaces might not use the same exact connector every time.
SATA
I'm sure you guys know about this, it's super common and it's been used in drives for years, though it is designed for slower/older mechanical Hard Drives.
[4]It has a limit of up to 6 gigabits per second in SATA 3 the latest version, so it is kind of slow and it also has lower latency because it was not designed in the first place with SSD, so it does work with SSD and if you don't need anything more than 6 gigabits, then it'll work. For those maximum speeds, you're gonna need something different.
PCI Express (PCIe)
This is also called “Expansion Bus” which is basically just a system for connecting different components in the computer. Universal Serial Bus or USB is for connecting things. The thing with PCI Express is that it’s much faster and you use this for things like graphics cards which has the big slot on the motherboard, you're probably familiar with it but you can actually use the PCIe interface for other things besides graphics cards and you can use it for storage.
[5]The speed of a PCIe connection will depend on how many so called lanes it's using, one lane of PCI Express is referred to as “x1” and that is just basically one set of connectors however, if it's a bigger slot, it may combine multiple of those and get faster speeds. For example, there's x4, x8 and the maximum size is x16 which is about the size you would see if you were to plug in a graphics card.
There are different updates and versions to PCIe, the latest one is PCIe 3.0, so one lane of PCI Express currently can do 8 gigabits per second (x1 = 8Gbps). As I mentioned, SATA can only do 6 gigabits per second and only one lane of PCI Express can do already more than that but there's even more lanes you could use.
PCIe 3.0
x1 = 8 Gbps
x4 = 32 Gbps
x8 = 64 Gbps
x16 = 128 Gbps
That’s a huge amount of data, you can use however much you wanted depending on how much the device needs. It's also good to know that every update to PCIe doubles the bandwidth, so PCI Express 4 will double all of those values.
It is important to know those 2 different interfaces “SATA and PCI Express” when I’m going to explicate about everything in the rest of this article and when you're going out to buy a Solid State Drive because you might see that it has a certain speed but if you're not connecting it the right way, you'll understand why you might not get the maximum speed unless you’re doing it right.
The different shapes and sizes of Solid State Drives (SSD)
The most common one you saw would probably be a 2.5 inch drive and that is ever since they had Hard Drives. They have 2.5 inch Hard Drives and SSDs as well but most of these are going to be SATA drives, so typically if you see one it's just gonna be a maximum of that 6 gigabits per second for SATA 3 and that will give you a theoretical maximum of about 750 megabytes per second.
[6]However, in real life with overhead, you might only see around 600 megabytes per second as a maximum if you're using a regular 2.5 inch SATA SSD which most of those are. If we want those maximum speeds, we're gonna have to start using PCI Express.
PCI Express expansion card form factor for an SSD
This is literally just an SSD you plug directly into one of those PCI Express ports that is like the slot which you put into a graphics card. This is going to give you as much speed as you need, so typically it'll probably be either x4 or x8 and you’ll not be limited by the connection at all.
[7]Like I mentioned, most of these are just gonna be x4, that's 32 gigabits per second more than you would need in most SSDs, although there are some like this super expensive intel SSD that plugs directly into an x8 slot or uses x8 lanes.
You can plug it into a bigger slot even if it doesn't use all the pins but that's like several thousand dollars, so you can spend the money if you want but x4 is probably enough.
M.2 Form Factor
This form factor is pretty interesting, it's relatively new and you may have heard of this, it also refers to M.2 Connector, it's kind of both the form factor and a connector. This does actually use PCI express and it uses four lanes although it also supports SATA and USB 3 interestingly, so you don't necessarily have to plug in an SSD into an M.2 slot although it does suit that very well.
[8]The nice thing about M.2 drives is they're very small, I mean the connector itself is very small, so usually the whole drive along with it although you need to keep in mind that this connector is attached directly to the motherboard.
If you don't have an M.2 connector on your motherboard, you're not going to be able to use one of these unless you were to get some sort of expansion card that goes into a PCI Express port and then you connect the M.2 that way but at that point, you may as well probably just get a direct PCI Express SSD and forget about the adapter.
M.2 drives are getting a lot more popular, this is usually reserved for the really high end SSDs. For example, you can typically get multiple gigabyte speeds of read and write out of it and one specific example is Samsung's 960 pro.
[9]This will give you a read speed of 3500 megabytes a second and a write speed of 2100 megabytes a second and you can use that full speed because it does use that x4 PCI Express interface, using the M.2 connector. Remember we made the distinction earlier on.
U.2 Connector
This is basically like a Enterprise-grade M.2 and it is also using a PCIe Express x4 (4 lanes) although it is also compatible with SAS and SATA. If you need to use one of those, you can but the real point is to use it with PCI Express.
[10]When you see some U.2 Enterprise-grade SSDs, they're usually 2.5 inch. For example, there are some made by Intel and you might be wondering why you would use this over M.2, What’s the advantage?
Well, if you think about it, an M.2 connector is attached directly to the motherboard, there's not a lot of space whereas U.2 connector actually use a wire connector, you could probably see where I'm going with this. You can fit a lot more drives on the same motherboard because instead of having to fit the entire M.2 or SSD on the motherboard, you can just put a bunch of different connectors and then spread out the Hard Drives externally so you can fit a lot more.
[11]The form factor of a 2.5 inch tribe is better suited for a data center, it's easier to hot-swap whereas with M.2, you typically have to like either snap it off or unscrew it, it's not very realistic if you're dealing with a ton of drives. Typically, you are not going to see any U.2 connectors on a consumer motherboard, maybe if it's like a really top-end one. Although if you really want to use one, you can actually get M.2 to U.2 adapters that plug into the slot and then you can use an SSD that use that if you want.
In conclusion
Those are the different connectors and form factors, I’m going to go over the different protocols or logical interfaces in the next part of the article. You can think of this like the software whereas PCI Express and SATA can be thought of like hardware. I hope you enjoyed this part of the article, so stay tuned for the next part and don’t forget to hit that upvote button below.
References: 1 - 2 - 3 - 4 - 5
Image sources: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11
