Clarification of terminology: SSD vs M.2, vs PCIe vs. NVMe

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It's about that time when there are dramatic improvement in the area of storage. Yay! But as usual, there are so many terms and the products haven't quite (IMHO) shaken out. So please check me here and help me clarify a few areas I'm not too clear on.

SSD: attaches via 6GB/s (Max) SATA. Product: Samsung Evo 850 and Evo 850 Pro

M.2: Motherboard interface for SATA? Or does this allow for direct (PCIe) connection as well?) I know it somes in several different form factors (ugh). Not sure about a product as I've never used this in a build.

PCIe: 2-lane and 4-lane variants that utilize a PCIe slot and has substantial faster transfer rates. However, often the interface is "faked" (for want of a better word and the data actually goes through the SATA stack at some point in time. The early generations of OCZ PCIe drives used this to my knowledge.

NVMe: the new, native PCIe attachment for really blistering fast storage. The more recent Samsung and Intel NVMe drives comes to mind.


Have I got this about right?
 

middlemarkal

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m.2 : sata or nvme, depending on the motherbaord can be 1 or 2 lines of pcie2 or up to 4 lines pcie3, available on motherbaords or pcie card.

the rest seems good

look here for the latest on SSD:

http://www.thessdreview.com/
 

joex444

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Sort of, but not fully. SSD simply means a permanent storage device based on flash memory, hence it doesn't include USB sticks (though you can convert SSDs to USB 3.0 with a 2.5" USB3.0 <-> SATA enclosure).

How it connects is another matter. SATA refers to, currently, SATA-III with 6Gb/s (600MB/s -- remember SATA uses 8b10 encoding so 1 byte is represented by 10 bits -- essentially the 8 bits we want and 2 parity bits; the key part is that 10 bits = 1 byte on the SATA protocol, but 1 byte written to the drive takes up 8 bits).

SSDs can come in, basically, three formats. One is the 2.5" drive, which is *typically* connected via SATA and therefore limited to 6Gbps. Another is the M.2 form factor, which comes in various lengths. These, of course, require an M.2 connector which is found on many modern motherboards, especially at the higher tier, and many modern laptops. This, however, is merely a form factor! The way that the drive connects to the system, electrically, can be *either* SATA or PCIe. And within PCIe, there's two variants - it's the new PCIe 3.0 x4 one that we're interested in as that offers 32Gb/s. The other electrical connections are, and have been, essentially pointless. The older PCIe variant is faster than 6Gb/s but not substantially so like 32Gb/s is.

Another form factor is the PCIe card, which may simply be a board that converts a PCIe slot into an M.2 port, particularly with the PCIe 3.0 x4 variant this is more of a physical adapter than anything electrical. Other PCIe cards have the flash memory directly attached to them (this is actually more common).

NVMe stands for Non-Volatile Memory Express and is simply a protocol for getting flash memory to operate as an SSD via PCIe. It implies nothing about the form factor. In fact, some 2.5" drives *are* NVMe and operate via a U.2 connection (which can be adapted from an M.2 port via a special M.2 card).

Certainly moving forward, the thing that people are going to lust after is the 32Gb/s NVMe connection, be it in M.2 form factor or 2.5" drives with non-SATA connections like U.2.
 
SSD is a generic term and includes all of the others' you listed. The early ones and large portion of the current ones use the same form factor as hard drives and those models typically connect via the standard motherboard SATA connectors.

M.2 is actually a form factor specification (physical connections, card size, etc.) and there are some variations. M.2 drives can support more than one logical interface such as legacy SATA, SATAe/AHCI, and/ or SATAe/NVMe. There may be some now that support PCIe. The bottom line is you have to really dig into specific drives specs to see what they support and whether your mobo supports it also.

PCIe uses PCIe slots and, again, you need to look into the specific drives and compatibility with your mobo/graphics card setup regarding the lanes used.

NVMe can be either SATAe or PCIe based (I think) but I haven't looked into it very far yet.

The different configurations are geared towards different operating environments, i.e. consumer, workstation, datacenter etc.
 
What is changing everything below is Skylake CPU's and the Z170 chipset. This is a generational update. Something you only see once a decade, if that. Some of the pieces that are intended to be used as parts of this, such as an Intel Optane SSD using Intel Xpoint (cross point) memory, will not be out until sometime next year. But it will bring the same kind of speed increases over SSDs that SSDs brought over hard drives. In addition, it will be far more durable than NAND is. In addition, the XPoint chips are far more dense than DDR, so this means much smaller chips will hold far higher amounts of storage.

Hard drive throughput: 100MB/sec
NAND SSD throughput: 550MB/sec
XPoint SSD throughput: estimated 5500MB/Sec



SSD: attaches via 6GB/s (Max) SATA. Product: Samsung Evo 850 and Evo 850 Pro.

SSD means Solid State Device. Essentially a Non-Volatile Memory Device. With the Z170 chipset, SATA Express can do 10GB/sec while SATA III will remain at 6GB/sec. The Non-Volatile Memory in an SSD is called NAND. XPoint and other upcoming memory types can be used as well.

M.2: Motherboard interface for SATA? Or does this allow for direct (PCIe) connection as well?) I know it somes in several different form factors (ugh). Not sure about a product as I've never used this in a build.

M.2 so far uses the same NAND that the SATA III SSD's use. This may change at some point. With the Z170 chipset, M.2 with 4x PCIe lanes are available, and as many as 3 of these could be on a single motherboard. Each one would support up to 32GB/sec. If the correct 12 lanes are used (out of a list of 26 lanes the chipset offers), multiple M.2 ports can be setup as raid now under Intel RST.

PCIe: 2-lane and 4-lane variants that utilize a PCIe slot and has substantial faster transfer rates. However, often the interface is "faked" (for want of a better word and the data actually goes through the SATA stack at some point in time. The early generations of OCZ PCIe drives used this to my knowledge.

This is the old way of doing a PCIe SSD.

NVMe: the new, native PCIe attachment for really blistering fast storage. The more recent Samsung and Intel NVMe drives comes to mind.

This is the new way of doing a PCIe SSD. The NVMe (Non-Volatile Memory express) was created by Intel to support their upcoming XPoint (cross point) NVM SSD cards as bootable SSD's with extremely low latency. These cards will become available in 2016. Fortunately, it also can be used with NAND, so companies can and are creating bootable NAND based cards today, and getting ready to ship them.

NVMe is the interface that is going to let Intel Optaine storage cards redefine the SSD market. The Intel Optane cards will literally will be so much faster than todays SSDs, that it will provide the same kinds of increases in data throughput that SSD's produced over hard drives. The chart at the top of this post shows IOPS increasing by over 7x at a queue depth of 1, which is about what a gamer or home user normally utilizes on an SSD. So I am trying to be conservative, and say that the Intel XPoint NVMe cards will have data throughput of (only) 5500MB/sec. I honestly feel that it will actually be 20% to 30% higher than that, but we do need to wait for the cards to become available, and then test them on a Z170 motherboard. This will happen sometime in 2016.
 

albert 89

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Unfortunately, Intel's Optane will be a ripoff. And that's putting it mildly. An SSD or M.2 etc in an optimal raid configuration will be cheaper in several orders of magnitude.
 

JaredDM

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I know this isn't going to be the longest or most thorough answer, but I'm hoping to just concisely point you in the correct direction.

SSD: Just refers to any Solid State Drive typically using NAND flash memory. What you described in your original post was SATA not SSD. The Samsung SSDs come in both SATA and M.2 varieties.

PCIe: An interface which is faster and has lower latency than SATA. Originally used mainly for video cards, now most motherboards have several of these high speed channels including some dedicated to an M.2 SSD slot. PCIe can potentially be much faster than SATA lanes, though not all SSDs are fast enough to take advantage of this.

M.2: A new form factor slot on the motherboard for smaller SSDs. It can have SATA and/or PCIe lanes going to the slot. If the SSD and Motherboard both support PCIe, it'll generally use that. If either doesn't it may revert to the internal SATA channel.

NVMe: Is not an "attachment" at all. Rather it is a new communications protocol that allows for faster data transfers than before, especially with high end SSDs. It is actually a replacement to AHCI protocol which had been a replacement to the IDE protocol.
 
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