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Samsung Unveils First PCIe 3.0 x4-Based M.2 SSD, Delivering Speeds of Over 2GB/s
Deathspawner writes: Samsung's SM951 is an unassuming gumstick SSD — it has no skulls or other bling — but it's what's underneath that counts: PCIe 3.0 x4 support. With that support, Samsung is able to boast speeds of 2,150MB/s read and 1,550MB/s write. But with such speeds comes an all-too-common caveat: you'll probably have to upgrade your computer to take true advantage of it. For comparison, Samsung says a Gen 2 PCIe x4 slot will limit the SM951 to just 1,600MB/s and 1,350MB/s (or 130K/100K IOPS), respectively. Perhaps now is a bad time to point out a typical Z97 motherboard only has a PCIe 2nd Gen x2 (yes, x2) connection to its M.2 slot, meaning one would need to halve those figures again.
No! I would say: FORTUNATELY I don't think that's going to happen.
2000MB/s is still one or two orders of magnitude slower than DDR3/4 (between 20000 and 60000MB/s) so I clearly don't want direct mapping.
Let the OS cache the SSD sectors in RAM pages and everything will be fine (and from the user point of view, that won't change anything)
This SSD is not a PCIe slot form-factor card like you may be used to seeing. It is a M.2 form-factor SSD (see the picture of the drive in the articles). So having a x16 or even a x4 standard PCIe plugin slot will not help at all. The motherboard has to list that has a M.2 slot that is capable of PCIe gen3 speeds.
Bollocks. An M2 to PCIE adapter is twenty bucks.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
The big news here is that this is pretty much the first consumer available SSD that supports NVME! There are some super-expensive pro devices that do NVME but they likely alone cost more than your whole high-end gaming rig.
http://en.wikipedia.org/wiki/NVM_Express
NVME is the interface that replaces AHCI, which was designed for spinning rust devices that can really only read and write one bit at a time. Flash based devices don't have to wait for moving parts and thus can access many things at once.
AHCI was designed for magnetic drives attached to SATA. NVME is explicitly designed to accommodate fast devices directly connected to PCI express. Take a look at the comparison table on the wikipedia page linked above. Multiple, deep, queues and lots of other features to remove bottlenecks that don't' apply to flash based storage.
How useful NVME currently is to consumers, though, is different. Only really new operating systems can boot from NVME devices. (Windows 8.1 or later. Don't know the current state of linux support but I bet at least someone's got a patched version of the kernel and grub if there's not mainline support already) And most most motherboards don't properly support NVME booting yet either. (Ive heard reports that some do with a BIOS/firmware update but it's currently really spotty)
1. These are sequential speeds. They're only relevant when you're dealing with large files. Unless your job is working with video or disk images or other large files, the vast majority of your files are going to be small, and the IOPS matters more. 130k/100k IOPS is really good, but only about a 10%-20% improvement over SATA3 SSDs. It translates into 520/400 MB/s at queued 4k read/writes best case. Current SATA3 drives are already surpassing 400 MB/s queued 4k read/writes.
2. Like car MPG, the units here are inverted from what actually matters. You don't say "gee, I have 5 gallons in the tank I need to use today, how many miles can I drive with it?", which is what MPG tells you. You say "I need to drive 100 miles, how many gallons will it take?" which is gal/100 miles. Yes they're just a mathematical inverse, but using the wrong one means the scaling is not linear. If you've got a 100 mile trip:
A 12.5 MPG vehicle will use 8 gallons
A 25 MPG vehicle will use 4 gallons (a 4 gallon savings for a 12.5 MPG improvement)
A 50 MPG vehicle will use 2 gallons (a 2 gallon savings for a 25 MPG improvement)
A 100 MPG vehicle will use 1 gallon (a 1 gallon savings for a 50 MPG improvement)
See how the fuel saved is inversely proportional to the MPG gain? As you get higher and higher MPG, it matters less and less because MPG is the wrong unit. If you do it in gal/100 miles it's linear. (This is why the rest of the world uses liters / 100 km.)
An 8 gal/100 mile vehicle will use 8 gallons.
A 4 gal/100 mile vehicle uses 4 gallons (a 4 gallon savings for a 4 gal/100 mi improvement)
a 2 gal/100 mile vehicle uses 2 gallons (a 2 gallon savings for a 2 gal/100 mi improvement)
a 1 gal/100 mile vehicle uses 1 gallon (a 1 gallon savings for a 1 gal/100 mi improvement)
The same thing is true for disk speeds. Unless you've got a fixed amount of time and need to transfer as much data as you can in that time, MB/s is the inverse of what you want. The vast majority of use cases are a fixed amount of MB that needs to be read/written, and the time it takes to do that is what you're interested in because that's time you spend twiddling your thumbs. If a game needs to read 1 GB to start up:
A 100 MB/s HDD will read it in 10 sec
a 250 MB/s SATA2 SSD will read it in 4 sec (a 6 sec savings for a 150 MB/s improvement)
A 500 MB/s SATA3 SSD will read it in 2 sec (a 2 sec savings for a 250 MB/s improvement)
A 1 GB/s PCIe SSD will read it in 1 sec (a 1 sec savings for a 500 MB/s improvement)
This 2 GB/s PCIe SSD will read it in 0.5 sec (a 0.5 sec savings for a 1000 MB/s improvement
Again, the actual time savings is inverted from the units we're using to measure. We really should be benchmarking HDDs and SSDs by sec/MB.
A 10 sec/MB HDD will read 1 GB in 10 sec
A 4 sec/MB SATA2 SSD will read it in 4 sec (a 6 sec savings for a 6 sec/MB improvement)
A 2 sec/MB SATA3 SSD will read it in 2 sec (a 2 sec savings for a 2 sec/MB improvement)
A 1 sec/MB PCIe SSD will read it in 1 sec (a 1 sec savings for a 1 sec/MB improvement)
This 0.5 sec/MB PCIe SSD will read it in 0.5 sec (a 0.5 sec savings for a 0.5 sec/MB improvement)
That's nice and linear. You see that the vast majority of your speedup comes from switching from a HDD to a SSD - any SSD, even the old slow first gen ones. The next biggest savings is switching to a SATA3 SSD. Beyond that the extra speed is nice, but don't be mislead by the huge MB/s figures - the speedup from PCIe drives will never be as big as those first two steps from a HDD to a SATA SSD. Manufacturers just report performance in MB/s (instead of sec/MB) because it exaggerates the importance of tiny increases in time saved, and thus helps them sell new and improved (and more expensive) products. Review sites also report in MB/s because if you report in sec/MB, the benchmark graphs are boring and the speedup from these shiny new SSDs is barely perceptible.