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Bringing SSD Performance to the DIMM form factor

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Re: Bringing SSD Performance to the DIMM form factor

#151

Post by mark-r »

ghshephard wrote: post #126
zanny wrote: post #37

Earlier quoted context omitted.

Flash is really closing in on disk, though. If costs continue to halve biannually, and capacities keep rising like they do, they might intersect around 12 - 16TB in five to ten years.

Sometime before that, I'm guessing in about 3 years +/- 6 months, the capacity+performance advantages of flash will reach a point where spinning disk doesn't make sense, volumes of flash being ordered start to accelerate, spinning disk volumes plateau, and investments in developing the technology adjust accordingly (more investment in improving flash, less in spinning disk) I would be willing to wager that new models…

I think it will happen much sooner than that. Flash doesn't have to match the price/GB of hard drives, it just has to match at the minimum viable system level. A lot of people could survive with 120GB, and that number goes up drastically when you hit 240GB. When the price of those SSDs reaches the hard drive floor of about $50, hard drives will become a niche product appealing only to those who actually need multiple terabytes.

Re: Bringing SSD Performance to the DIMM form factor

#152

Post by jhallenworld »

bitL wrote: post #38

What would be the advantage of this comparing to PCIe/M.2 PCIe SSDs? Is it all about reduced latency, i.e. very small reads/writes would benefit?

One big benefit is that it provides a way to add flash to systems with no PCIe slots, like blade servers.

Re: Bringing SSD Performance to the DIMM form factor

#153

Post by digi_owl »

luma wrote: post #40
NamTaf wrote: post #3

I can't wait to see the programming paradigm of memory vs permanent storage begin to blur in the next 5 or so years. It's going to make some major assumptions about how you program stuff change quite significantly and it's really exciting.

HP is already working on this with what they're calling "The Machine". They're writing a new OS around the new storage technologies with the understanding that it might not make sense to separate RAM from disk pretty soon here. They've also suggested that they'll be porting versions of Linux and Android to this platform. Of course, all of this is pretty marketing heavy and not a lot of details have been released, so…

I seem to recall that early Palm devices used run-in-place, but i don't recall if they were able to maintain state if there was a power loss.

Re: Bringing SSD Performance to the DIMM form factor

#154

Post by hadoukenio »

ghshephard wrote: post #126
zanny wrote: post #37

Earlier quoted context omitted.

Flash is really closing in on disk, though. If costs continue to halve biannually, and capacities keep rising like they do, they might intersect around 12 - 16TB in five to ten years.

Sometime before that, I'm guessing in about 3 years +/- 6 months, the capacity+performance advantages of flash will reach a point where spinning disk doesn't make sense, volumes of flash being ordered start to accelerate, spinning disk volumes plateau, and investments in developing the technology adjust accordingly (more investment in improving flash, less in spinning disk) I would be willing to wager that new models…

> I would be willing to wager that new models of laptops in 2020 with spinning disk will be uncommon

How about more like 2015. You're already forgetting MacbookAir/Chromebook/Ultrabook crowd are slowly taking over (which have no spinning disks).

Re: Bringing SSD Performance to the DIMM form factor

#155

Post by rsync »

13 wrote: post #149
IgorPartola wrote: post #137

This is sort of the opposite of the RAM-based battery backed drives [1]. I can see this being immediately useful for things like large database servers: instead of re-priming caches on reboots you just have them already warmed up. You can also suddenly have a whole lot more "RAM" at the cost of its speed. I do have a hard time picturing what this will look like if it was as fast as traditional RAM. If I can store eve…

I do wish the iRam had stuck around longer. The 4GB limit makes it practically useless today, but a modern version of the same would be incredibly useful for some workloads.

Aren't there plenty of other PCIe ram-cards ?

Like http://ddrdrive.com/ ?

I didn't think there was any shortage of these kind of devices - especially given their common use in ZFS workloads as a SLOG.

Re: Bringing SSD Performance to the DIMM form factor

#156

Post by rsync »

IgorPartola wrote: post #137

This is sort of the opposite of the RAM-based battery backed drives [1]. I can see this being immediately useful for things like large database servers: instead of re-priming caches on reboots you just have them already warmed up. You can also suddenly have a whole lot more "RAM" at the cost of its speed. I do have a hard time picturing what this will look like if it was as fast as traditional RAM. If I can store eve…

"However, I wonder how the modern UNIX OS will work with a system like this without block devices at all."

I don't think that's how it works - I think you get a special driver that presents the fast-storage-in-dimm-slot as a block device. So you still have a block device, it's just faster.

Right ?

Re: Bringing SSD Performance to the DIMM form factor

#157

Post by jhallenworld »

jpgvm wrote: post #31
toyg wrote: post #17

Earlier quoted context omitted.

> Does this act like a stick of memory or an SSD? Like an SSD. > Is it just using the memory controller as a super fast parallel bus? Afaik, it's this.

Technically it acts like memory. The dev kit comes with a device driver that makes it look like a block device though, which would be analogous to something like NVMe.

Well at the interface level it has to look like memory since it's attached to a memory bus. But that does not mean it looks like a single large DIMM. There is no way in the DRAM protocol to delay a transaction while data is read from the flash chips into the buffer, so you need a protocol on top of the simple memory model.

"nvDIMMs" on the other hand do look like and are as fast as plain memory. Disadvantage is that they are not big.

Re: Bringing SSD Performance to the DIMM form factor

#158

Post by 13 »

rsync wrote: post #155
13 wrote: post #149

Earlier quoted context omitted.

I do wish the iRam had stuck around longer. The 4GB limit makes it practically useless today, but a modern version of the same would be incredibly useful for some workloads.

Aren't there plenty of other PCIe ram-cards ? Like http://ddrdrive.com/ ? I didn't think there was any shortage of these kind of devices - especially given their common use in ZFS workloads as a SLOG.

I couldn't find any when I looked recently, even the one you've linked to is quite old (2009) and has the same 4GB (presumably 32bit) limit. If they were more common and in more realistic sizes I'd love to get my hands on one.
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