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http://www.hardocp.com/article/2015/03/24/where_ssd_market_headed_in_2015/#.VYTrWflVhBc
Here Comes NVMe
The AHCI command set, which supplanted ATA so long ago, wasn’t designed with SSDs in mind, and is highly inefficient when communicating with low-latency PCIe SSDs. This leads to wasted CPU cycles, poor performance under parallel I/O, and a general inability to get the most out of a PCIe SSD. The NVMe standard was created to solve these problems.
Non-Volatile Memory Host Controller Interface, or NVM Express (a.k.a. NVMe), has been a hot buzzword in storage for some time. Without getting too technical- it is a standard designed specifically for SSDs communicating through PCIe, and enables these drives to reach peak performance with lower CPU utilization. Coupled with the higher throughput and lower overhead of the PCIe 3.x bus (vs. PCIe 2.0), this is a highly optimized solution.
If your motherboard has BIOS support for NVMe, you should be able to boot from the NVMe drive. While NVMe support has been very limited so far, with consumer NVMe drives just beginning to hit the market, check with your motherboard manufacturer for a BIOS update. Windows 8.1 has built-in support for NVMe- earlier versions will require a driver. NVMe SSDs will be offered as M.2 cards, SATA Express drives, and PCIe half and full-height cards.
Form Factors and Interfaces
M.2
Without the need for platters, SSD devices are just a printed circuit board, which could theoretically be made into all sorts of interesting, flat shapes. In the time of Ultrabooks, NUCs, and Mini-ITX, the M.2 (formerly NGFF) form factor is a common and compact format for SSDs. M.2 drives are available as double- or single-sided cards, and replace the older mSATA standard while offering a large degree of form factor and interface diversity.
Current M.2 cards are 22m wide, and available in lengths of 30-110mm. Most of the SSDs that you’d see for desktop use will be the 2260 or 2280 size (60mm and 80mm long, respectively). The M.2 connector itself can carry a few different buses, including PCIe, USB 2.0/3.0, SATA, I2C, and audio, depending on how it is keyed. For SSDs, you may see key types of A (PCIe x2), B (PCIe x2 + SATA), E (PCIe x2), or M (PCIe x4 + SATA), with M being the choice for high performance drives.
At present, motherboards with more than one M.2 slot are extremely rare, but there are inexpensive (~$20) adapters available to use M.2 drives in a PCIe slot without a performance penalty. NVMe support will depend on the motherboard’s BIOS and the drive itself.
SATA & SATA Express
The SATA interface that you’ve come to know and love isn’t quite going away, but it is growing up. SATA Express ("SATAe") adds PCIe connectivity to the SATA standard- it’s a new connector, but backwards compatible. 2-lane PCIe 2.0 SATAe links have theoretical max bandwidth of 10Gb/s, and 2-lane PCIe 3.0 SATAe offers 16Gb/s. Both of these greatly exceed SATA 3.0’s 6.0Gb/s transfer rate, while offering NVMe if supported by both the drive and BIOS. SATA Express will be seen primarily on 2.5" SSDs, but could make its way to 1.8" devices as well. Motherboard support for SATAe is still relatively uncommon, and consumer-oriented drives using the standard barely exist, but both will change going forward.
PCIe Add-In Cards
Most of the current enthusiast PCIe SSDs are half-length cards (half or full-height), using two 8 PCIe 2.0 lanes. As manufacturers roll out consumer and enthusiast NVMe cards, the inevitable shift to the much faster PCIe 3.x will take place. Considering both the overhead of the interface and the transfer rate, PCIe 3.x is about twice as fast as PCIe 2.0, so a PCIe 2.0 x8 card will have approximately as much throughput as a PCIe 3.x x4 card.
As mentioned earlier, most of the PCIe SSDs that are currently available have a SATA chip (or several, in RAID) onboard, and are not actually native PCIe solutions. By definition, any of the upcoming NVMe solutions will be native PCIe devices.
Booting to PCIe SSDs used to be hit or miss, but it’s mostly sorted out on current motherboards, such as those using the Intel 9-series chipsets.
USB 3.1/Thunderbolt
I’m putting our two external standards together because you can’t much talk about one without the other. USB 3.1 is a great leap forward in many ways, offering 10Gb/s transfer speeds (matching Thunderbolt), reversible Type-C cables, and up to 100W of power supplied through the port. Most importantly, USB 3.1 will be highly available and inexpensive, while Thunderbolt devices continue to be mostly a niche product that’s almost nonexistent on PCs. Since the USB 3.1 announcement, major manufacturers have announced a large number of drives and enclosures, and we’ll be taking a look at how it stacks up against Thunderbolt in the near future.
The Bottom Line
If you’ve got an I/O-bound workload, your life is probably about to get a good bit easier, and without having to spend thousands of dollars on enterprise-grade PCIe SSDs. The arrival of NVMe is game-changing, and it will be interesting to see how BIOS support evolves over the coming months. Meanwhile, as the top tier drives will become some flavor of PCIe-based solutions, we may see further downward price pressure in the SATA SSD space.
If you’re already happy with your SSD, then there probably won’t be a compelling need to move to a PCIe SSD. Still, you could take advantage of the changing market to snap up an inexpensive SATA SSD for your backup machine, or family member. Odds are that they will notice that their computer is suddenly faster, and we will all have one fewer windmill at which to tilt.
Here Comes NVMe
The AHCI command set, which supplanted ATA so long ago, wasn’t designed with SSDs in mind, and is highly inefficient when communicating with low-latency PCIe SSDs. This leads to wasted CPU cycles, poor performance under parallel I/O, and a general inability to get the most out of a PCIe SSD. The NVMe standard was created to solve these problems.
Non-Volatile Memory Host Controller Interface, or NVM Express (a.k.a. NVMe), has been a hot buzzword in storage for some time. Without getting too technical- it is a standard designed specifically for SSDs communicating through PCIe, and enables these drives to reach peak performance with lower CPU utilization. Coupled with the higher throughput and lower overhead of the PCIe 3.x bus (vs. PCIe 2.0), this is a highly optimized solution.
If your motherboard has BIOS support for NVMe, you should be able to boot from the NVMe drive. While NVMe support has been very limited so far, with consumer NVMe drives just beginning to hit the market, check with your motherboard manufacturer for a BIOS update. Windows 8.1 has built-in support for NVMe- earlier versions will require a driver. NVMe SSDs will be offered as M.2 cards, SATA Express drives, and PCIe half and full-height cards.
Form Factors and Interfaces
M.2
Without the need for platters, SSD devices are just a printed circuit board, which could theoretically be made into all sorts of interesting, flat shapes. In the time of Ultrabooks, NUCs, and Mini-ITX, the M.2 (formerly NGFF) form factor is a common and compact format for SSDs. M.2 drives are available as double- or single-sided cards, and replace the older mSATA standard while offering a large degree of form factor and interface diversity.
Current M.2 cards are 22m wide, and available in lengths of 30-110mm. Most of the SSDs that you’d see for desktop use will be the 2260 or 2280 size (60mm and 80mm long, respectively). The M.2 connector itself can carry a few different buses, including PCIe, USB 2.0/3.0, SATA, I2C, and audio, depending on how it is keyed. For SSDs, you may see key types of A (PCIe x2), B (PCIe x2 + SATA), E (PCIe x2), or M (PCIe x4 + SATA), with M being the choice for high performance drives.
At present, motherboards with more than one M.2 slot are extremely rare, but there are inexpensive (~$20) adapters available to use M.2 drives in a PCIe slot without a performance penalty. NVMe support will depend on the motherboard’s BIOS and the drive itself.
SATA & SATA Express
The SATA interface that you’ve come to know and love isn’t quite going away, but it is growing up. SATA Express ("SATAe") adds PCIe connectivity to the SATA standard- it’s a new connector, but backwards compatible. 2-lane PCIe 2.0 SATAe links have theoretical max bandwidth of 10Gb/s, and 2-lane PCIe 3.0 SATAe offers 16Gb/s. Both of these greatly exceed SATA 3.0’s 6.0Gb/s transfer rate, while offering NVMe if supported by both the drive and BIOS. SATA Express will be seen primarily on 2.5" SSDs, but could make its way to 1.8" devices as well. Motherboard support for SATAe is still relatively uncommon, and consumer-oriented drives using the standard barely exist, but both will change going forward.
PCIe Add-In Cards
Most of the current enthusiast PCIe SSDs are half-length cards (half or full-height), using two 8 PCIe 2.0 lanes. As manufacturers roll out consumer and enthusiast NVMe cards, the inevitable shift to the much faster PCIe 3.x will take place. Considering both the overhead of the interface and the transfer rate, PCIe 3.x is about twice as fast as PCIe 2.0, so a PCIe 2.0 x8 card will have approximately as much throughput as a PCIe 3.x x4 card.
As mentioned earlier, most of the PCIe SSDs that are currently available have a SATA chip (or several, in RAID) onboard, and are not actually native PCIe solutions. By definition, any of the upcoming NVMe solutions will be native PCIe devices.
Booting to PCIe SSDs used to be hit or miss, but it’s mostly sorted out on current motherboards, such as those using the Intel 9-series chipsets.
USB 3.1/Thunderbolt
I’m putting our two external standards together because you can’t much talk about one without the other. USB 3.1 is a great leap forward in many ways, offering 10Gb/s transfer speeds (matching Thunderbolt), reversible Type-C cables, and up to 100W of power supplied through the port. Most importantly, USB 3.1 will be highly available and inexpensive, while Thunderbolt devices continue to be mostly a niche product that’s almost nonexistent on PCs. Since the USB 3.1 announcement, major manufacturers have announced a large number of drives and enclosures, and we’ll be taking a look at how it stacks up against Thunderbolt in the near future.
The Bottom Line
If you’ve got an I/O-bound workload, your life is probably about to get a good bit easier, and without having to spend thousands of dollars on enterprise-grade PCIe SSDs. The arrival of NVMe is game-changing, and it will be interesting to see how BIOS support evolves over the coming months. Meanwhile, as the top tier drives will become some flavor of PCIe-based solutions, we may see further downward price pressure in the SATA SSD space.
If you’re already happy with your SSD, then there probably won’t be a compelling need to move to a PCIe SSD. Still, you could take advantage of the changing market to snap up an inexpensive SATA SSD for your backup machine, or family member. Odds are that they will notice that their computer is suddenly faster, and we will all have one fewer windmill at which to tilt.
