Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Intel’s Plans for 3DXP DIMMs Emerge

realworldtech.com

Post reply on HN
Print view View original

41–50 of 75 posts

Re: Intel’s Plans for 3DXP DIMMs Emerge

#41

Post by robotresearcher »

gravypod wrote: post #32
jzelinskie wrote: post #20

It 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?

Zero serialization. Imagine installing a program and always having it "running". It may be swapped out but littetally everything in it is ready to go when you switch to it's window.

We have that right now, do we not? You don't have to quit apps except on reboot.

Except that many apps are so buggy you have to restart them often in practice. NVM won't change that, sadly.

Re: Intel’s Plans for 3DXP DIMMs Emerge

#42

Post by mozumder »

freeone3000 wrote: post #37
mozumder wrote: post #26

Earlier quoted context omitted.

Probably the optimal use of this technology is databases, since they rely most on random access to large persistent data. Any operating system that's designed around this technology is probably going to look like a database. Basically, boot to Postgres and all "files" are now SQL tables, stored in NVDIMM. Indexes are in DRAM, and critical nodes are in cache. All data (system and user) is organized and opinionated: Al…

Hey, that sounds line a mainframe... I wonder what it'll take to get zOS running on commodity.

Mainframes have always led the way in computer architecture.

Re: Intel’s Plans for 3DXP DIMMs Emerge

#43

Post by WhitneyLand »

jzelinskie wrote: post #20

It 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?

Persistent dara structures? Well yes, but that’s just the tip of the iceberg. There other scenarios like powerful real-time analytics that could benefit from 100TB of RAM immediately.

100TB systems at RAM speeds are theoretically possible without this new memory. For,example 64-bit systems could easily provide enough address space.

The problem is practically speaking, server systems limit address bit capabilities quite often. And other problems still remain, not the least of which is the crazy price for 100TB of DDR4,physical slots, etc. The price would be crazy even for most enterprise projects.

So yes this new generation of memory will be disruptive, but also keep in mind even though it’s faster than SSDs, that’s not nearly enough. I’m not positive, but IIRC correctly it’s still 2 or 3 orders of magnitude slower than conventional memory.

Does that mean this new wave od persistent RAM it’s not useful and awesome? Not at all, I’ve already started using it.

But it does mean it’s still at the stage where you have to analyze your scenarios carefully, see if it’s a good for your architecture and environment, and benchmark your particular stack to verify assumptions and make sure it’s help you the best way it can.

Re: Intel’s Plans for 3DXP DIMMs Emerge

#44

Post by fh973 »

While 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.

Re: Intel’s Plans for 3DXP DIMMs Emerge

#45

Post by glangdale »

dragontamer wrote: post #31
glangdale wrote: post #23

Earlier quoted context omitted.

Seriously, 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…

> 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.

I don't think "computers stay up a long time these days" is an argument against doing OS research on order-of-magnitude-faster, byte-addressable persistent storage.

We seem to be doing pretty well with a bunch of abstractions from the 1970s, as well as with the idea of just building giant trapdoors into our hardware whenever these abstractions fail (e.g. most databases, DPDK in the network space, etc). It's not a crisis. It just seems like a pretty good time to do some basic OS research (aside from all the usual headwinds for that, e.g. massive complexity of underlying hardware, difficulty finding meaningful workloads for a "toy" OS, etc).

Re: Intel’s Plans for 3DXP DIMMs Emerge

#47

Post by dragontamer »

stouset wrote: post #38
dragontamer wrote: post #31

Earlier quoted context omitted.

> 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.

On 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 up…

> None of this has anything to do with fast persistent storage, but I sincerely hope the era of 500-day uptimes is waning.

On the contrary. Persistent memory means that infinite uptime is the future. Which, as you note, is difficult. Resetting the OS every now and then to a known state is a good practice, although disruptive to a lot of workflows.

If anything, I consider your post to be an argument AGAINST persistent memory.

Re: Intel’s Plans for 3DXP DIMMs Emerge

#48

Post by throwaway2048 »

wtallis wrote: post #22
AtlasBarfed wrote: post #21

The initial release was really underwhelming, given the hype around this. So my personal (uninformed) expectations is just incremental improvement to the initial product.

Moving 3D XPoint memory from the peripheral IO bus to the memory bus is way more than an incremental improvement.

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.

Re: Intel’s Plans for 3DXP DIMMs Emerge

#49

Post by rasz »

QuadrupleA wrote: post #27

I 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.

no, unless Everything else in your system retains state, that includes all the registers in every single chipset/controller/processor.

Re: Intel’s Plans for 3DXP DIMMs Emerge

#50

Post by infogulch »

mozumder wrote: post #26
jzelinskie wrote: post #20

It 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?

Probably the optimal use of this technology is databases, since they rely most on random access to large persistent data. Any operating system that's designed around this technology is probably going to look like a database. Basically, boot to Postgres and all "files" are now SQL tables, stored in NVDIMM. Indexes are in DRAM, and critical nodes are in cache. All data (system and user) is organized and opinionated: Al…

The entire information world is either a database or a cache (or communication between them), layered on top of each other over and over. Every new storage technology typically ends up being yet another layer as either database or cache (or both). This case is pretty unique in that it can actually serve to remove a layer: ram (typically a cache) is not necessary if nvs is viable at the same speeds. But in general new storage tech just adds another layer, which the software world reacts to by rushing in as if to fill a void by creating new software to take advantage of it which ends up being... another database or cache, often with similar tradeoffs to the layers of cache/database surrounding it. In the limit, I see more and more layers of cache/database until they merge into some kind of continuous data/cache field with a continuous tradeoff gradient between size and latency.
Post reply on HN