Earlier quoted context omitted.
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.
They can afford to, considering how much one costs :)
Intel’s Plans for 3DXP DIMMs Emerge
61–70 of 75 posts
Re: Intel’s Plans for 3DXP DIMMs Emerge
#62While 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. The…
I 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
I 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.
Re: Intel’s Plans for 3DXP DIMMs Emerge
#63It 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?
> Another thought: As potentially paradigm changing technology like this becomes available will it ever make sense to redesign the OS?
Realistically, it's implications are much bigger for applications that depend heavily on persistent storage, like databases. They make tons of assumptions about persisting to block storage, whereas 3DXP could enable them to function entirely "in memory", so all that block storage specific optimization they have is now working against them. I'm just generalizing here, though.
Re: Intel’s Plans for 3DXP DIMMs Emerge
#64One 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.
Re: Intel’s Plans for 3DXP DIMMs Emerge
#65It 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 qui…
There will, almost inevitably, be someone who needs 101TB of memory. Then you get back to the same place where you need to scale out instead of up. If you asked cloud architects for cheaper, lower latency network or faster more expemsive storage you'd probably get the former most of the time.
Spark already works nicely with 100+TB datasets, and those can sit in memory across a thousand spot instances. Technology like tidalscale's hyperkernel can also merge together multiple systems into a single addressable memory space at the OS level so that you can run non-distributed applications across multiple commodity machines (like a reverse VM).
If 3d xpoint can give competitive price and speeds to tradional DRAM, then it will have a place in the market. Nobody has seen pricing yet nor benchmarks for these. For Intel however, this could increase their component share from CPU/chipset/network/storage to also include memory. That is pretty compelling since it's a market they haven't monetizes (not counting memory controllers) since the early days of Intel.
Re: Intel’s Plans for 3DXP DIMMs Emerge
#66Earlier 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.
Your ideas around uptime are still in the 70's. Systemd updates require reboots. Then there's Spectre and Meltdown BIOS updates, gotta reboot for those. Oh and the SSD and NIC firmware as well.
To think we formerly only had one devil in glibc. Now everything is constantly being updated and it's fine. We've moved on from the uptime as phallic measuring stick mantra. Patch, reboot, and stay secure.
Re: Intel’s Plans for 3DXP DIMMs Emerge
#67Price. 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.
Re: Intel’s Plans for 3DXP DIMMs Emerge
#68Earlier 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.
But traditional operating systems still assume RAM contents is volatile (because currently it is), most filesystems assume disks are glacially slow etc. A traditional spinning rust HDD has an effective latency of ~10 ms. The NVME version of the 3DXP has an effective latency of ~50 us, or two orders of magnitude better. Not sure how low the DIMM version will go, but maybe another order of magnitude? If so, we're talki…
> But traditional operating systems still assume RAM contents is volatile (because currently it is)
RAM is only volatile on startup. Certainly not when a VM hibernates and comes back.
Re: Intel’s Plans for 3DXP DIMMs Emerge
#69Earlier quoted context omitted.
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…
Persistent memory might enable those sorts of uptimes, but it doesn't inherently mandate it.
Re: Intel’s Plans for 3DXP DIMMs Emerge
#70Earlier quoted context omitted.
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…
You forgot, frequent rebuilds kill off any intrusion as the world reflashes -- unless they get into IoT or microcontroller packages.
I did mention that it makes it harder for an attacker to keep a foothold in your infrastructure, but I think I wasn't as clear as I wanted to be.
But yeah, it's bad that an attacker has been able to get to a critical system, but it's a phenomenal defense if any of their beacons or remote access tools last at most a few hours or days before being wiped. This makes an attacker's life much harder.