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3D Xpoint memory: Faster-than-flash storage unveiled

bbc.com

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Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#81

Post by codebook »

mmf wrote: post #56
zxcv123 wrote: post #50

Earlier quoted context omitted.

Power consumption of DRAM is high, what are you talking about? DRAM requires constant refresh -- the whole reason DRAM can be high-density if because it is a 1-T cell with a trench capacitor -- but the capacitor needs to be refreshed on a synchronized basis (hence SDRAM) -- that was the big innovation. And yes, array size affects latency but so does the underlying process technology (much more so across technologies)…

As I did not have the numbers fresh in memory (apparently I needed a refresh ;) ) I googled for dram data sheet and got the first ddr3 PDF (Hynix). Quick, and very dirty math suggests that -refresh power is on the order of milliwats per Gigabyte -memory access is on the order of 0.1W per GB per second For refresh power, let's face it: it's puny. Regarding the active power, I have yet to see anything (off chip and thi…

you overlooked refresh time, which is around 7~8 ms. So, in order to keep the DRAM data alive, DRAM should consume a few tenths of Watt per Gigabyte per second, it is considerable amount of power.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#82

Post by witty_username »

codebook wrote: post #81
mmf wrote: post #56

Earlier quoted context omitted.

As I did not have the numbers fresh in memory (apparently I needed a refresh ;) ) I googled for dram data sheet and got the first ddr3 PDF (Hynix). Quick, and very dirty math suggests that -refresh power is on the order of milliwats per Gigabyte -memory access is on the order of 0.1W per GB per second For refresh power, let's face it: it's puny. Regarding the active power, I have yet to see anything (off chip and thi…

you overlooked refresh time, which is around 7~8 ms. So, in order to keep the DRAM data alive, DRAM should consume a few tenths of Watt per Gigabyte per second, it is considerable amount of power.

watt per second makes little sense in this context

watt != energy

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#83

Post by xxs »

jjoonathan wrote: post #65
mmf wrote: post #55

Earlier quoted context omitted.

Not shits and giggles, it's access to the array: subarray and word line decoding plus sense amp time. Find me a technology that does not need all these and I'll bow to you (and invest in your startup :D).

SRAM? I'm only half kidding. As a complete industry outsider it doesn't seem ridiculous to think that SRAM could do to DRAM what SSDs did to HDDs. Alas, I have no idea what the economics + trends are and I never did more than dabble in semiconductor engineering/physics so I will only ever find out after the fact.

>>As a complete industry outsider it doesn't seem ridiculous to think that SRAM could do to DRAM what SSDs did to HDD

SRAM needs 6 transistors per bit, DRAM 1transisitor+1capacitior. SRAM just doesn't scale and it's very expensive.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#84

Post by ykorman »

nly wrote: post #40
Animats wrote: post #37

So what do we do with it? We have two models of storage - volatile working storage, and things that simulate disk drives. It's not clear what to do with persistent randomly addressable storage at DRAM speed. Having to go through an OS and a file system to access a few bytes kills the performance advantage of such devices. Making the device look like RAM makes it too easy to mess up. We need something in between, prob…

I think the only distinction you need to make is memory where transactions make sense (user data), and where they don't (program state). I can see a scenario where opening a file for writing works just like mmap[0] with MAP_PRIVATE, i.e. you get blockwise copy-on-write, except everything will persist as if everything on your filesystem was under a VCS like git. I reckon just like volume management, encryption and sna…

see pmem.io

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#85

Post by rasz_pl »

wmf wrote: post #59
rasz_pl wrote: post #53

Dear Micron, brace for a mother of all patent lawsuits from HP.

HP certainly convinced the public that they have a monopoly on NVM. Too bad their technology isn't that successful.

HP itself is convinced they have a monopoly on the idea. Technology doesnt have to be successful if you have an army of lawyers working for you. Who wants to bet HP will sue just to keep Micron from shipping products for a couple of years.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#86

Post by dooptroop »

russdill wrote: post #72
ncr100 wrote: post #71

Earlier quoted context omitted.

The video presentation mentioned "resistive". I'm not a memory nerd. Does that fact from their disclosure help at all narrow what this type of memory can be best categorized as? https://intel-micron-webcast.intel.com/webcast

There is an entire family of memory elements who's resistance is modified in order to store data. RRAM/ReRAM, CBRAM, PCM, MRAM, as well as many others.

I suppose "resistive" in this context relates to the method used to read the memory, not so much how this change of resistance is implemented.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#87

Post by dooptroop »

witty_username wrote: post #82
codebook wrote: post #81

Earlier quoted context omitted.

you overlooked refresh time, which is around 7~8 ms. So, in order to keep the DRAM data alive, DRAM should consume a few tenths of Watt per Gigabyte per second, it is considerable amount of power.

watt per second makes little sense in this context watt != energy

But Watt * second IS energy.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#88

Post by mmf »

codebook wrote: post #81
mmf wrote: post #56

Earlier quoted context omitted.

As I did not have the numbers fresh in memory (apparently I needed a refresh ;) ) I googled for dram data sheet and got the first ddr3 PDF (Hynix). Quick, and very dirty math suggests that -refresh power is on the order of milliwats per Gigabyte -memory access is on the order of 0.1W per GB per second For refresh power, let's face it: it's puny. Regarding the active power, I have yet to see anything (off chip and thi…

you overlooked refresh time, which is around 7~8 ms. So, in order to keep the DRAM data alive, DRAM should consume a few tenths of Watt per Gigabyte per second, it is considerable amount of power.

A few corrections:

-refresh period is more like 32-64ms

-refreshing is way (way) cheaper than streaming data out since you refresh an entire word line, and you do not pay io cost, which is a significant fraction of the cost of accessing dram.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#89

Post by mmf »

witty_username wrote: post #82
codebook wrote: post #81

Earlier quoted context omitted.

you overlooked refresh time, which is around 7~8 ms. So, in order to keep the DRAM data alive, DRAM should consume a few tenths of Watt per Gigabyte per second, it is considerable amount of power.

watt per second makes little sense in this context watt != energy

It's W/GBps, or if you prefer simplifying J/GB. I like the former better, power and bandwidth are handier in real life computer science.

Re: 3D Xpoint memory: Faster-than-flash storage unveiled

#90

Post by coldtea »

wtallis wrote: post #32
rosser wrote: post #30

Earlier quoted context omitted.

"Bit-addressable". I don't think this suffers from the same issues that NAND does with successive writes. The other articles I'm seeing after a quick search also suggest a three order of magnitude increase in write endurance.

Yes, if you read what I wrote I mentioned the three orders of magnitude increase in write endurance as compared with NAND. But when paired with the three orders of magnitude increase in performance, that means it takes the same number of hours to burn it out. And a NAND device without wear leveling can be burned out in less than a day of heavy use. Bit addressability has absolutely nothing to do with endurance. NOR f…

>Yes, if you read what I wrote I mentioned the three orders of magnitude increase in write endurance as compared with NAND. But when paired with the three orders of magnitude increase in performance, that means it takes the same number of hours to burn it out.

Only in some bizarro world where "three orders of magnitude increase in performance" also means "we'll write three orders of magnitude more data into it".

Loads are about use cases, not about how fast you can fill a disk. If my company produces 1TB analytics info per day it wont suddenly produce 1000TB just because I can write to the disks we buy faster.

Of course being able to fill it faster also opens up some new, more heavy, use cases. But for any existing use cases, we'd be writing the SAME data volumes we do now, just 1000 times as fast and with 1000 times the endurace.

And even if we write 100 the data we do now, we still get 10 times the endurance.

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