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Intel’s Plans for 3DXP DIMMs Emerge
- oh_sigh 8y agoWhy can't we just put a battery onto DRAM that maintains state if the power goes out, and be done with it?
- ggm 8y agoWe do on RAID cards. It has limits. -G
- hetman 8y agoBecause the power consumption to keep DRAM refreshed is fairly high so you'd need a pretty big battery, and because it would still be more expensive than 3DXP. It's just not practical for most use cases.
- amelius 8y agoI figured that, but can we have some numbers here?
- steve19 8y agoThat is how storage worked on PDAs back in the day with volitile memory. Let's the batteries completely die or change them incorrectly and you lost your data. Let's not go back to those days!
- wmf 8y agoDRAM is not that dense; you can fit 128 GB of DRAM or 512 GB of XPoint on a DIMM. XPoint is also supposed to be cheaper than DRAM.
- jcoffland 8y agoBattery backed DRAMM has been around for a decade or more.
- IshKebab 8y agoYou mean like suspend-to-RAM?
- jzelinskie 8y agoIt seems obvious in retrospect, but persistent memory adds a pretty exciting new advantage for persistent data structures. Another thought: As potentially paradigm changing technology like this becomes available will it ever make sense to redesign the OS?
- glangdale 8y agoSeriously, yes. If there was ever a time to rethink OS design, surely this is it. That being said, operating systems like Linux tend to capture most of the value from these kind of advances - often by dint of being able to simply 'get out of the way' if a sufficiently important user space process wants access to the device. But one would suspect that things have changed sufficiently from the 1970s to warrant a ground-up rethink. Core counts, distributed systems (the Plan 9 folks already too a swing at this in the 90s), nearly ubiquitous graphics/GPGPU accelerators, persistent memory, nearly ubiquitous access to 64-bit address spaces (at least for desktop and most phones) - you'd think something would change about design. I don't work in the area so I don't know what that is...
- dragontamer 8y ago> Seriously, yes. If there was ever a time to rethink OS design, surely this is it. Why? Traditional servers are persistent: they never turn off. 500+ days of uptime is typical. And today, with VMs which at worst... hibernate... it seems like "never turning off" might be the norm.
- stouset 8y agoOn the contrary, as a security professional I’d be thrilled if servers had a lifespan of hours instead of weeks or months. Reimaging VMs/containers/machines from scratch frequently gives so many advantages. When OS, system, or library updates happen, you can easily launch replacement servers on the updated stack, put them in the rotation, and decommission the old ones. This is so much simpler than trying to run OS upgrades in-place across an entire fleet. The longer a machine has been running between reboots, the lower my belief in its odds of upgrading and restarting cleanly. Further, this regularly tests your load balancing setup and pretty much fundamentally gives you capacity to scale up and down as load permits. Problems will be discovered early on, instead of during crunch time when you have to scale or when a few of your machines go offline during peak hours. Security-wise, you don’t just get the benefit of fast, regular updates. But you also get assurances that users haven’t left stale data like unencrypted database exports, PII dumps, etc. lying around. Go on a long-lived machine some day and check out users’ home directories. That shit is a gold mine if someone who wants to do harm gets on your systems. Not to mention regular reimaging makes it harder for an attacker to establish a permanent foothold in your infra. None of this has anything to do with fast persistent storage, but I sincerely hope the era of 500-day uptimes is waning.
- deleted 8y ago[deleted]
- Ocha 8y agowebsite times out. Also, this story hasnt been reported by any other news source. Is there some other site I can see the story at?
- tarlinian 8y agoIt's not a news story...mostly analysis/predictions. (If you're talking about generic announcements of XPoint DIMMs that was in the news at the end of may: https://www.anandtech.com/show/12828/intel-launches-optane-dimms-up-to-512gb-apache-pass-is-here https://www.anandtech.com/show/12828/intel-launches-optane-d...)
- jaytaylor 8y agoFound a copy freshly archived today @ archive.org: http://web.archive.org/web/20180723220131/https://www.realworldtech.com/intels-3dxp-dimms/ http://web.archive.org/web/20180723220131/https://www.realwo...
- hughes 8y agoSadly this only archived the first of four pages.
- vbezhenar 8y agoremoved
- dkanter 8y agoThank you for being a gentleman (or gentlewoman)!
- dkanter 8y agoWebsite should be up, I just rebooted AWS :)
- stephengillie 8y agoI have coworkers who believe AWS is "Amazon WorkSpace" and complain "my AWS is slow, please reboot my AWS."
- gravypod 8y agoThere's so much amazing stuff I could do with this. Imagine persistent redis? Huge huge pages? Booting from a DIM? The possibilities are endless.
- AtlasBarfed 8y agoThe initial release was really underwhelming, given the hype around this. So my personal (uninformed) expectations is just incremental improvement to the initial product.
- wtallis 8y agoMoving 3D XPoint memory from the peripheral IO bus to the memory bus is way more than an incremental improvement.
- throwaway2048 8y agoSays the company that claimed it would be 1000x faster than NAND flash, it isn't, and moving the location of the bus isn't going to change that.
- wtallis 8y ago> Says the company that claimed it would be 1000x faster than NAND flash, it isn't, and moving the location of the bus isn't going to change that. Using the IO bus instead of the memory bus is exactly why existing Optane products haven't delivered latency that's 1000x better than NAND flash. NVMe transactions take at least 5-10µs even with DRAM as the SSD media rather than NAND flash or 3D XPoint. Moving to the memory bus is a prerequisite to 3D XPoint fulfilling those original performance claims.
- QuadrupleA 8y agoI guess in a theoretical NVM-only system you could pull the plug at any time, and instantly resume it when the power is back on? If I'm reading right though the latency of 3DXP is somewhere in the 10-20us ballpark, still 100-1000x slower than DRAM.
- sp332 8y agoYes but it's also cheaper than DRAM. You could resume after pulling the plug as long as things are consistent. If you commit data in the wrong order you could have trouble!
- rasz 8y agono, unless Everything else in your system retains state, that includes all the registers in every single chipset/controller/processor.
- randyrand 8y agoThe CPU has internal state as well that won’t be persisted - at the very least the registers. Would be to save them when you notice power loss.
- inamberclad 8y agoOn a few occasions I've found myself in the presence of a senior engineer at a large defense company who would never stop talking about how persistent memory will change everything forever. Fair enough, but he'd go on about it in the weirdest ways. I think his impression is that the CPU registers would also be nonvolatile. I'm concerned that guy might be a few electrons short of a full orbital.
- vbezhenar 8y agoSaving and restoring CPU registers and flushing caches into non-volatile memory doesn't require much time or energy.
- monocasa 8y agoSpecifically, you can normally do something like that between when you notice the power dropping and when it drains too much and you have to shut down.
- zeusk 8y agoShouldn't be hard, all they have to do is a light context switch to idle thread on power loss interrupt and make the idle thread externally re-entrable.
- Milner08 8y agoThis is perfectly possible. I used to work on something that did just this but at the time used a small battery and an SSD to quickly dump the volatile state before power loss. This meant we had to limit the amount of volatile data that could be stored in ram (due to the transfer rate and up time on the battery). We were eagerly awaiting 3DXP DIMMs so that we could remove that limit. It really will have a big impact on critical systems where any data loss is not acceptable.
- fh973 8y agoWhile there are some analytics workloads that will benefit tremendously, the main use case will be improving server utilization. Currently RAM is not a compressible resource like CPU. However many applications don't have a fixed or if easily predictable RAM footprint and so you have to overprovision. Swap has been there to solve that but with its performance impact, it often can't be used for server applications. These DIMMs will blur the boundary between memory and swap and make swap again viable.
- dmichulke 8y ago> and make swap again viable You shouldn't work in political marketing :-)
- tpetry 8y agoI dont get your logic. CPUs have a finite number of instructions they can do in a timeframe, its not compressible. In the other one someone could compress the memory, works great for storage. Sure, it‘ll be slower but compressing seldomly used memory pages like macOS does is indeed possible
- oblio 8y agoI think his point is that you can "run" a large amount of applications at the same time on a CPU. It will execute everything, albeit slowly. This might not be acceptable for performance concerns, but it's doable. He's not talking about actual data compression in RAM. Because even with compression, with current OSes, if you try to fit more than 20GB of data, let's say becoming 10GB compressed, into 5GB of RAM, it's not possible. You have to swap and at that point your performance is completely gone. The performance gap between an overloaded CPU and swapping is humongous. One is annoying or slightly troublesome, the second is a death knell.
- kristianp 8y agoIs there any tech that's faster than DRAM and cheaper than SRAM? There's a need to fill that gap.
- AtlasBarfed 8y agoL2/L3 cache?
- kristianp 8y agoThat's SRAM usually.
- grogers 8y agoOne interesting thing for databases is that as nonvolatile storage latency decreases, traditional btrees get more attractive relative to newer log-structured designs. Especially if the write endurance is increased as well over current SSDs.
- wtallis 8y agoOr to put it another way: there's not a lot of reason to have two layers of log-structured storage. Your SSD already needs its own log-structured flash translation layer, and if that's tuned properly for your database workload, then another layer of the same kind of thing may not help much.
- ksec 8y agoPrice. Remember the current DRAM is 2.5x the price of what is was two to three years ago. So the XP DIMM being 4x cheaper then DRAM Now isn't that much different if DRAM dropped back to its median level.