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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.
It's curious how many relatively recent high-end PCs from prestige-brands don't have PCIe 3.0 slots. Alienware are a particular offender here - they were very slow adopters, quite possibly because a lot of their customers don't actually think to check for this when speccing up a machine.
That said, it's questionable how much it really matters in the real world at the moment. Performance tests on the latest video cards (which can take advantage of PCIe 3.0) have found very little performance gap between 3.0 and 2.0 (and even 1.0) with the likes of the Nvidia 980. The gap is most apparent at extremely high (150+) framerates - which is unlikely to constrain the average gamer, who probably just turns up the graphical settings until his PC can't sustain his target framerate (probably somewhere in the 40-60fps rate) any more.
Last time I used a RAM drive, it was on the contents a floppy disk. My brother was sick of slow compile times and worked out how to use the university DOS computers to produce a RAM drive. Autoexec.bat created it and copied his files into it, and then it ran like greased lightning.
But that was back when 1.44Mb of RAM was a lot and he was lucky enough to be somewhere where every computer had that spare.
Last time I saw it when when making a single-floppy Linux distribution that copied itself into RAM because it was often used on diskless workstations. Just like almost every Ubuntu install disk can do now if you select Live CD from the boot menu.
But on ordinary desktop OS? Since Windows 95, RAMDisks have been dead. Since then, we've been using RAM better to cache all recent filesystem accesses. There's very, very, very, very little that will ever benefit from a RAMDisk over just having that RAM as filesystem cache automatically anyway. You still have to read the data from permanent storage anyway, and once you've done that, it's in RAM until you start to fill up RAM. Read it often enough and it will never drop out of the cache. If you're not reading it often enough, why the hell bother to RAMDisk it?
And you lose NOTHING if the machine dies mid-way. With a RAMDisk, any changes you make are gone.
Please. Stop spreading absolute "gold-plated-oxygen-free" junk advice like this.
Anyone who wants to do this can do it with any bit of freeware on any machine. But why they would bother is beyond me. Hell, next you'll be telling me to enable swapfiles and put them on the RAMDisk....
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.