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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

#91

Post by coldtea »

wtallis wrote: post #35
acqq wrote: post #7

Earlier quoted context omitted.

If what they claim is true, it has the potential to be actually cheaper than both DRAM and NAND, based on the density. The biggest disadvantage at the moment is that is so new that we don't know much. What can be read from the announcement: it's not as rewritable as DRAM: only up to 1000 more writes than NAND. It's also slower than DRAM. But it seems better than NAND in all aspects.

It's nowhere near as dense as NAND. It's just a bit denser than DRAM.

>It's nowhere near as dense as NAND.

Err, they mention several times the density of NAND.

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

#92

Post by coldtea »

anotherangrydev wrote: post #9

Always the same thing. >1000X faster, 1000X cheaper! Then "No, you can't buy one right now, but you will be able to do it "soon". And, no it won't actually be 1000X faster neither 1000X cheaper because blah blah blah..."

I think you're conflating R&D press releases (which are often vapour) with announcements of actual production, which are few and far between, and almost always pan out.

Second, those 1000x faster and 1000x cheaper. I've been around a few decades, and we DO have 1000x faster and 1000x cheaper stuff now.

CPUs are 1000x the speed of 1980 CPUs.

1GB of RAM would cost you a house back in 1990.

A 1TB disk would cost you half a skyscrapper plus take 2-3 houses to house back in the day.

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

#93

Post by wtallis »

coldtea wrote: post #91
wtallis wrote: post #35

Earlier quoted context omitted.

It's nowhere near as dense as NAND. It's just a bit denser than DRAM.

> It's nowhere near as dense as NAND. Err, they mention several times the density of NAND.

They claim 10 times the density of DRAM, which falls quite short of the density of NAND.

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

#94

Post by mslusarz »

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…

http://pmem.io/nvml/ with DAX

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

#95

Post by emmanueloga_ »

"At that point in time, there was an 8:1 price/GB differential between the 512 GB SSDs and the 500 GB HDDs. On the smaller drives, the ratio was 4:1." [1]

If anything I'm hoping the introduction of a competing new technology will make higher capacity SSDs cheaper.

1: http://www.zetta.net/blog/ssds-replace-hdds/

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

#96

Post by hipsterrific »

coldtea wrote: post #92
anotherangrydev wrote: post #9

Always the same thing. >1000X faster, 1000X cheaper! Then "No, you can't buy one right now, but you will be able to do it "soon". And, no it won't actually be 1000X faster neither 1000X cheaper because blah blah blah..."

I think you're conflating R&D press releases (which are often vapour) with announcements of actual production, which are few and far between, and almost always pan out. Second, those 1000x faster and 1000x cheaper. I've been around a few decades, and we DO have 1000x faster and 1000x cheaper stuff now. CPUs are 1000x the speed of 1980 CPUs. 1GB of RAM would cost you a house back in 1990. A 1TB disk would cost you hal…

Not only do we have stuff 1000x faster/cheaper than before, but 3D XPoint is backed by intel and micron, both have colluded for decades on how to develop faster, cheaper, durable storage.

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

#97

Post by witty_username »

mmf wrote: post #89
witty_username wrote: post #82

Earlier quoted context omitted.

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.

Ah, it made sense now.

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

#98

Post by jjoonathan »

xxs wrote: post #83
jjoonathan wrote: post #65

Earlier quoted context omitted.

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.

Thanks for trying to be helpful, but this is both the most common and least believable explanation among those that I keep hearing. A constant factor between 3 and 6 kills SRAM's viability? DRAM is already over-provisioned by a factor of 2-4 even at the middle of the consumer spectrum just to support the "use case" of someone who can't be bothered to close their tabs. Going back to the hand-wavey analogy, SSDs stormed the scene with a ~50x constant factor disadvantage:

http://www.kitguru.net/components/ssd-drives/anton-shilov/sa...

If the only thing standing between SRAM and DRAM were a constant factor of The most convincing explanation I've heard is that caches are so damn good at hiding latency that getting rid of row open/close just doesn't matter. A few minutes of googling suggests that they often run at a 95% hit rate on typical workloads and a 99% hit rate on compute workloads. You would still need a cache even with main memory as SRAM to hide transit-time, permission checking, and address translation latency, so SRAM main memory wouldn't actually free up much die space, it would just make your handful of misses a bit faster (well, it would free up the scheduler / aggregator, but not the cache itself). The reason why I called this one "most convincing" rather than "convincing" is that even with a 99% hit rate a single miss has such atrocious latency that it would seem to matter.

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

#99

Post by TheLoneWolfling »

xxs wrote: post #83
jjoonathan wrote: post #65

Earlier quoted context omitted.

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.

That's a constant factor of what, 6? Less once you consider the capacitor and row refresh circuitry?

And yet I cannot purchase even a 1GB SRAM stick.

I don't see why that equates to "just doesn't scale". Can you elaborate?

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