Ddram disk – A PCIe card with 14x RAM slots • Hacker News Board

Re: Ddram disk – A PCIe card with 14x RAM slots

#11

Post by halJordan » Mon, May 30, 2022, 6:53 PM UTC

liminalsunset wrote: post #3

An underrated use case for this would be for storage of sensitive information. Information stored on a non volatile device is difficult to erase (Format NVM/ATA Secure require power cycle, hard drives require time to actually wile). Even if the data is encrypted, it is vulnerable to xkcd's "rubber hose decryption". With DRAM, the storage media itself is fairly volatile and power removal/memory content initialization…

Apple solved this problem at scale some time ago. Im not sure slamming ram on a pcie card is a better solution than including a piece of effaceable storage somewhere.

Re: Ddram disk – A PCIe card with 14x RAM slots

#12

Post by wtallis » Mon, May 30, 2022, 7:34 PM UTC

aeaa3 wrote: post #8

Is this for real? The store, which looks pretty amateurish, has no products for sale ("out of stock") and the prices are vastly too good to be true. DDR3 memory for 40c per gigabyte? Cheapest I can see on Amazon is 5 times that. 256GB of memory (plus the board itself) for $280? Not possible. Sorry, I don't believe it.

I'm also doubtful that a memory controller with the necessary pin count can even fit under that heatsink. 14 DIMM slots can't all be sharing just one or two 64-bit channels at anything approaching standard speeds and timings.

Re: Ddram disk – A PCIe card with 14x RAM slots

#13

Post by resonator » Mon, May 30, 2022, 8:59 PM UTC

There is a lot more technical information at http://ddramdisk.store/.

It's slower than RAM, runs at around full pcie 4x speed of 7GB/s but it upports way more capacity than most boards would allow.

Re: Ddram disk – A PCIe card with 14x RAM slots

#14

Post by Nexxxeh » Mon, May 30, 2022, 9:33 PM UTC

humanistbot wrote: post #2

What is the competitive advantage of this versus NVMe? Their 1TB ramdisk is $1000, while a Gen 4 NVMe PCI-e card gives the same speeds in a smaller and more standard format for $150-$200.

Write endurance I guess would be one.

Samsung 980 Pro is under warranty up to 600 TBW.

I don't know if that is external data written, or also includes whatever overhead the drive's internal processes have, which I imagine is higher when you run it near max capacity.

RAM has virtually unlimited write endurance.

I was interested for CCTV recording, as it can be murder on standard HDDs and consumer SSDs. Continuous writing at whatever the total bitrate of all cameras is, plus whatever index you're using, plus whatever clips its generating.

Ideally HDD for the constant, SSD for the clips and index.

I had a small (120GB) clip and index SSD drive start to struggle in a dirt-cheap non-critical system and found it had written 42TB in a year. Now part of that was poor configuration, but the drive was REALLY starting to struggle, throughput would occasionally drop off a cliff.

The system was battery backed, so a RAM disk would have been fine, and on triggering the UPS I'd have it just copy the contents to a fast HDD.

Re: Ddram disk – A PCIe card with 14x RAM slots

#15

Post by farkanoid » Mon, May 30, 2022, 9:36 PM UTC

aeaa3 wrote: post #8

Is this for real? The store, which looks pretty amateurish, has no products for sale ("out of stock") and the prices are vastly too good to be true. DDR3 memory for 40c per gigabyte? Cheapest I can see on Amazon is 5 times that. 256GB of memory (plus the board itself) for $280? Not possible. Sorry, I don't believe it.

Something seems a bit dodgy. The about page shows the top and bottom PCB layouts without any RAM sockets, only dozens of DDR RAM ICs soldered directly to the back of the card.

...Which would be fine, had I not stumbled upon (what seems to be) the original project[1], in Russian no less.

The blog shares the same block diagram, images and DDR PCB layout. There are no DDR RAM slots. Further, the slots are through-hole and not SMD, you wouldn't be able to attach a heatsink directly to the back of the card as shown in the images.

[1] https://habr.com/ru/post/567742/

Re: Ddram disk – A PCIe card with 14x RAM slots

#16

Post by jmalicki » Mon, May 30, 2022, 10:07 PM UTC

humanistbot wrote: post #2

What is the competitive advantage of this versus NVMe? Their 1TB ramdisk is $1000, while a Gen 4 NVMe PCI-e card gives the same speeds in a smaller and more standard format for $150-$200.

Speaking as someone who actually runs NVMe RAIDs for large-ish databases, the NVMe speeds quoted are usually only attainable for large sequential streaming loads. While they are not spinning disks with heads that need to seek, there is still very substantial random I/O overhead with SSDs, including NVMe. Even with a top of the line model like a Samsung 980 Pro, you might only get 5% the PCIe 4 bus speed with heavy random IO performance.

RAM has cachelines and such, but postgres reading 8k at a time isn't limited by that.

How to work something like this into Linux as say, a very fast swap device, is another question.

Re: Ddram disk – A PCIe card with 14x RAM slots

#17

Post by xbmcuser » Mon, May 30, 2022, 10:09 PM UTC

With ddr5 entering mainstream we will soon have a lot of used ddr3 and ddr4 modules available for cheap.

Re: Ddram disk – A PCIe card with 14x RAM slots

#18

Post by LinuxBender » Mon, May 30, 2022, 10:17 PM UTC

It seems these are not produced any more? [1] If someone is currently manufacturing a battery/capacitor backed memory card that accepts several DIMM's of the recent memory modules like 32GB+ ea. I would be interested. There should be benchmarks from a popular 3rd party reviewer.

[1] - https://superuser.com/questions/1508905/is-there-a-modern-ra...

Re: Ddram disk – A PCIe card with 14x RAM slots

#19

Post by rincebrain » Mon, May 30, 2022, 10:42 PM UTC

farkanoid wrote: post #15

aeaa3 wrote: post #8

Is this for real? The store, which looks pretty amateurish, has no products for sale ("out of stock") and the prices are vastly too good to be true. DDR3 memory for 40c per gigabyte? Cheapest I can see on Amazon is 5 times that. 256GB of memory (plus the board itself) for $280? Not possible. Sorry, I don't believe it.

Something seems a bit dodgy. The about page shows the top and bottom PCB layouts without any RAM sockets, only dozens of DDR RAM ICs soldered directly to the back of the card. ...Which would be fine, had I not stumbled upon (what seems to be) the original project[1], in Russian no less. The blog shares the same block diagram, images and DDR PCB layout. There are no DDR RAM slots. Further, the slots are through-hole a…

That doesn't seem to be the original, given that Google Translate translates the top of the article as "originally posted by" with a link to ddramdisk.tech, which 404s now, but originally [1] did not.

[1] - https://web.archive.org/web/20210714152011/https://ddramdisk...

Re: Ddram disk – A PCIe card with 14x RAM slots

#20

Post by namibj » Tue, May 31, 2022, 1:23 AM UTC

Nexxxeh wrote: post #14

humanistbot wrote: post #2

What is the competitive advantage of this versus NVMe? Their 1TB ramdisk is $1000, while a Gen 4 NVMe PCI-e card gives the same speeds in a smaller and more standard format for $150-$200.

Write endurance I guess would be one. Samsung 980 Pro is under warranty up to 600 TBW. I don't know if that is external data written, or also includes whatever overhead the drive's internal processes have, which I imagine is higher when you run it near max capacity. RAM has virtually unlimited write endurance. I was interested for CCTV recording, as it can be murder on standard HDDs and consumer SSDs. Continuous writ…

Given that WD sells comparable TLC in their dual-port PCIe3 NVMe zoned namespace SSD with 10x the spec-sheet total drive writer, I'm not surprised. These commands don't unnecessarily copy data.