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DDRamDisk: RAM disk, a disk based on RAM memory chips

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Re: DDRamDisk: RAM disk, a disk based on RAM memory chips

#121

Post by ksec »

loxias wrote: post #99
inasio wrote: post #82

Earlier quoted context omitted.

Are you talking about Optane/3D-XPoint? The physics behind it seemed insane to me, amazing that they got it to work. I heard that the NVME protocol was originally designed with it in mind

Yeah, that stuff. Was recently discontinued, Micron pulled out, there's been some articles about why. Eventually I guess we'll have CXL, which might catch on, but then there's the delay for software support. It's a shame so much of computing is locked in to the "local minima" of current architecture it's difficult to break out into a new area of the search space. It would be cool to play with a computer with persiste…

Well they were even more expensive than DRAM. It is unfortunate we still haven't find a way to further reduce the cost of DRAM. Or at least a roadmap / projection towards $1/GB in Cost.

Re: DDRamDisk: RAM disk, a disk based on RAM memory chips

#122

Post by blacklion »

PragmaticPulp wrote: post #58
JonChesterfield wrote: post #54

An interesting quirk of the later designs is they're bring your own ram. That might be a worthwhile thing to do with a pile of DDR3 from an old server. I think I've got 256gb or so in a draw somewhere that's otherwise unlikely to see any use. Lithium battery strapped to consumer chips - so you can basically ignore the volatility aspect (possibly in exchange for an exciting new fire risk, not sure how professionally b…

> An interesting quirk of the later designs is they're bring your own ram. That might be a worthwhile thing to do with a pile of DDR3 from an old server. I think I've got 256gb or so in a draw somewhere that's otherwise unlikely to see any use. The 256GB version is listed at $280. That's more than enough to buy the fastest 2TB SSDs on the market which will match the performance of this device for most real-world work…

I don't think you could buy fastest 2TB SSD for $280. More like $20'000 for 6TB.

Fastest SSDs are not Samsungs, ADatas, SunDisks or other "household" brands (yes, I know, that Samsung has enterprise models, without names, only with partnumbers, but even these models are not "fastest").

It is special brands, prices for which is not publicly available (or my google-fu is not strong enough).

Everything you buy for $280 will degrade when 75% full, and even sustained linear write will tank after first several tens of gigabytes, when SLC caches will be full. Not to mention random write with small blocks.

Special enterprise SSDs, like DataEngine T2HP, costs much, much more (and don't have 2TB models, looks like it starts from 4TB or even 6TB now, but still it is not like x2 or x3 to $280, it is more like x50).

Re: DDRamDisk: RAM disk, a disk based on RAM memory chips

#123

Post by blacklion »

PragmaticPulp wrote: post #58
JonChesterfield wrote: post #54

An interesting quirk of the later designs is they're bring your own ram. That might be a worthwhile thing to do with a pile of DDR3 from an old server. I think I've got 256gb or so in a draw somewhere that's otherwise unlikely to see any use. Lithium battery strapped to consumer chips - so you can basically ignore the volatility aspect (possibly in exchange for an exciting new fire risk, not sure how professionally b…

> An interesting quirk of the later designs is they're bring your own ram. That might be a worthwhile thing to do with a pile of DDR3 from an old server. I think I've got 256gb or so in a draw somewhere that's otherwise unlikely to see any use. The 256GB version is listed at $280. That's more than enough to buy the fastest 2TB SSDs on the market which will match the performance of this device for most real-world work…

On the other hand, one who could buy true enterprise SSD, will not buy this DDRamDisk from strange hobby-looking site :-)

Re: DDRamDisk: RAM disk, a disk based on RAM memory chips

#124

Post by peter_d_sherman »

mastax wrote: post #104
peter_d_sherman wrote: post #69

I like the idea of using multiple FPGAs to ["fanout"/"cascade"/"distribute"/"one-to-many proxy" -- choose the terminology you like best] the SM2262EN to multiple sticks of DDR3 RAM... I'd be curious though, if the SM2262EN itself couldn't be replaced by yet another FPGA, and, if so, if the FPGA used for that purpose could be the exact same type as the other four... If so -- then one could sort of think of that arrang…

You can implement an SSD controller in an FPGA. That's how all the early server SSDs were implemented. I think my Fusion ioScale was one of them. It's just an enormous amount of effort. This already looks like a huge amount of engineering to do for what must be a very niche product.

Define "an enormous amount of effort" ?

(What one person considers "effort" -- might very well be considered a relaxing and pleasurable and interesting exercise -- by another...

For example, some people hate Math and consider performing Mathematical operations "effort" -- whereas some people love Math and could spend all day at it(!) -- and find the whole process relaxing and stimulating!

It all depends on a given person's interest or disinterest, their affinity or aversion -- to a given line of endeavor...)

So, define "an enormous amount of effort" ?

Re: DDRamDisk: RAM disk, a disk based on RAM memory chips

#125

Post by ahmetozer »

Good approach but nowadays linux and embedded systems supports tmpfs and ramfs, I use this approach for my embedded device for a long time to not use sdcard storage life span.

due to space conecerts at ram, here is my third method of ramfs https://ahmetozer.org/containerized-distro.html

Re: DDRamDisk: RAM disk, a disk based on RAM memory chips

#126

Post by 95014_refugee »

cryptonector wrote: post #64
PragmaticPulp wrote: post #56

Interesting design. They use FPGAs to emulate NAND storage with DDR, then use a standard NAND SSD controller. It doesn't perform any better than fast NVMe SSDs for larger, sequential operations. However, it appears to be an order of magnitude faster for the random 1K read/write operations. It also has infinite durability relative to an SSD, though obviously your data isn't infinitely durable during a power outage sce…

But it must suffer from rowhammer.

NAND also suffers from read disturbance; since they are emulating NAND devices, it seems reasonable to assume the FTL in the controller will be tracking reads as well as writes and refreshing blocks accordingly.

Re: DDRamDisk: RAM disk, a disk based on RAM memory chips

#127

Post by mastax »

peter_d_sherman wrote: post #124
mastax wrote: post #104

Earlier quoted context omitted.

You can implement an SSD controller in an FPGA. That's how all the early server SSDs were implemented. I think my Fusion ioScale was one of them. It's just an enormous amount of effort. This already looks like a huge amount of engineering to do for what must be a very niche product.

Define "an enormous amount of effort" ? (What one person considers "effort" -- might very well be considered a relaxing and pleasurable and interesting exercise -- by another... For example, some people hate Math and consider performing Mathematical operations "effort" -- whereas some people love Math and could spend all day at it(!) -- and find the whole process relaxing and stimulating! It all depends on a given pe…

Point taken, and I expect it's relevant to the author as I doubt even they thought this project was the most monetarily profitable use of their time.

How much effort? I do not know precisely, not having done it before. The relevant NVMe specifications add up to about 1000 pages, which is actually less than I expected. I suspect implementing all of that would take a rather long time regardless, and that's just the host-interface protocols. The harder part, I believe, is the implementation of the controller log itself. I intuit this based on the large visible effort the SSD industry has spent on various hardware and firmware improvements over the last decade. I don't have a good way to summarize it. The question is how much of that effort is necessary when using DRAM rather than NAND? Maybe you don't need sophisticated ECC, bad block detecting, block remapping, garbage collecting, etc.

I am pretty confident, however, that the author knows more about it than I do and their conclusion has been that it's worth using an existing SSD controller.

Re: DDRamDisk: RAM disk, a disk based on RAM memory chips

#128

Post by peter_d_sherman »

mastax wrote: post #127
peter_d_sherman wrote: post #124

Earlier quoted context omitted.

Define "an enormous amount of effort" ? (What one person considers "effort" -- might very well be considered a relaxing and pleasurable and interesting exercise -- by another... For example, some people hate Math and consider performing Mathematical operations "effort" -- whereas some people love Math and could spend all day at it(!) -- and find the whole process relaxing and stimulating! It all depends on a given pe…

Point taken, and I expect it's relevant to the author as I doubt even they thought this project was the most monetarily profitable use of their time. How much effort? I do not know precisely, not having done it before. The relevant NVMe specifications add up to about 1000 pages, which is actually less than I expected. I suspect implementing all of that would take a rather long time regardless, and that's just the hos…

>I am pretty confident, however, that the author knows more about it than I do and their conclusion has been that it's worth using an existing SSD controller.

When an off-the-shelf SSD controller (as opposed to an FPGA which is much more auditable) is used for a commercial, mass-market SSD -- whoever is making that SSD -- is also putting the root-of-trust for that SSD user's data -- in the hands of the SSD controller manufacturer...

You sure that that SSD controller manufacturer didn't put a hardware backdoor in that SSD controller? You sure that that SSD controller manufacturer didn't embed a hidden "security processor" in the silicon? You sure that it won't covertly communicate your data over RF and/or near-field signals with other nearby similar "black box" electronic components?

Because I'm not!

I wasn't there when the SSD controller was designed, I wasn't there when the SSD controller was fabricated. Any off-the-shelf existing SSD controller is truly a Black Box to me...

Your argument is one of efficiency and expediency.

That's fine for 99% of the Corporations on the planet who value time and efficiency over doing things the harder, slower, less-profitable -- but more correct and ethical transparent way...

My argument is one of transparency, security, knowledge, "doing the homework" -- and understanding how systems truly work under the hood.

Your argument is correct for 99% of the people and corporations out there who value speed and "time-to-market" -- over all other virtues.

But your argument is not correct for 1% of people, and your argument is not correct for me -- for reasons explained above.

In summation, your argument is not wrong...

You are about 99% correct -- but not 100%...

Sure, I could buy a Tesla (or any completely assembled consumer product for that matter!) -- but then I would never have the satisfaction or the fun (or learning!) of trying to build my own!

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