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

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

ddramdisk.store

Post reply on HN
Print view View original

91–100 of 128 posts

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

#91

Post by simplotek »

JonChesterfield wrote: post #34
GordonS wrote: post #2

I don't have a use for this, but I enjoyed the detailed write-up! In these days of fast SSDs, are there still uses for a RAM disk, beyond extreme niches?

I use one for building C++. Granted that's a bit niche, but a tmpfs filesystem over the build directory keeps the load off the SSD. Haven't actually checked it's still faster for a while but it certainly used to be. Have been doing that for five years or so.

> I use one for building C++. Granted that's a bit niche (...)

Not niche at all. Using a RAM disk for building C++ applications is one of the oldest and most basic build optimization tricks around. It's specially relevant when using build cache tools like cache, which lead large C++ builds to no longer be CPU bound and become IO bound.

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

#93

Post by Dylan16807 »

Felger wrote: post #89
Dylan16807 wrote: post #62

Earlier quoted context omitted.

I think the question was more tuned to physical ram disks, but I'm not sure. Either way, how many terabytes were being written each day? And how much can your drive take? It looks like I could go pay $60 right now for 600TB of endurance, and $35 for 200TB of endurance. If you already have the extra ram than go for it but it doesn't seem like a setup to make on purpose. Maybe your backup system has far more writes tha…

(I was answering to the previous comment wondering if ramdisks still have any interesting usage nowadays.) About 150 TBW endurance on a 250 GB Samsung M.2 NVMe Evo 970+. On paper that is, but since it is the OS SSD with Windows Server 2022 STD (sole DC AD/DHCP/DNS/Hyper-V), in production, I won't take any risk. RAID 1 in this scenario would have changed nothing. On the side, I have 40 TB RAID10 for storage. So I canc…

Unless that server replaces a quarter of those files every day, the lesson I'm getting here is "Don't use C2 Backup agent".

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

#94

Post by numpad0 »

sandworm101 wrote: post #68
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…

>> infinite durability relative to an SSD Until the FPGA dies. Consumer-grade arrays are not eternal. Many have lifespans (>5% failure rate) as low as 2-5 years under regular use.

Perhaps durability can be clarified as infinite write endurance, which it has.

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

#95

Post by MayeulC »

I've really wanted something like that where I could just drop my old RAM sticks and use it as swap space.

It would be much better than flash-based solutions, both latency and endurance-wise, probably even over an USB link (3.1 and above speeds are pretty decent, even 3.0 would be enough for basic swap).

Bonus points for a DIMM slot that just accepts any generation (DDR2,3,4, not sure if that would be mechanically possible?). I retired some DDR4 sticks for higher frequency ones, but the 8GB DDR4-2400 stick I have in the drawer would be quite welcome as swap space on the 4GB soldered RAM laptop I am using...

I may have a go at it myself, I don't think the controllers would be too complex if writing a custom kernel driver, and targetting USB speeds.

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

#96

Post by jonsen »

dboreham wrote: post #80
rwmj wrote: post #12

Earlier quoted context omitted.

The concept is old as the hills, if you include static RAM. It was a common way for early digital synthesizers (early 80s) to store patches in battery backed SRAM. Even on removable cards.

My first encounter with the concept was in 1982 during the summer working at an electronics company. We used the then new 64K DRAMs in production so there was a ready supply of devices vendors had given us for evaluation. I built a 128KB memory board with bank selection logic then wrote a driver for the Flex OS (6809) to make that memory appear like a disk. Also built a similar board with (probably, long time ago..)…

> I built a 128KB memory board with bank selection logic then wrote a driver for the Flex OS (6809) to make that memory appear like a disk.

Oy! I could have written exactly that. What a coincidence :-) I also wouldn't claim invention. Maybe I heard of it, but I'd say the idea is pretty obvious. We made it possible for Flex to run to programs simultaneously and also do print spooling. (That's when I bought an HP 16C. Great help. Still have it.)

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

#97

Post by numpad0 »

matja wrote: post #42
qwerty456127 wrote: post #37

I wonder why this is not a commonly available and used thing. I have always wanted to use more RAM chips than my CPUs/motherboards would support, put all the swap on RAM chips, probably also load the whole OS&apps system drive into RAM this way (hint for your board: add an SSD it would load from, single-time on turn-on) and only use a persistent storage drive for my actual data files. Using more RAM instead of HDD/SS…

> The amount of RAM you were allowed to plug into a PC motherboard always felt like the most annoying limitation You could always get motherboards that took more RAM, just not ones that taking your typical gaming CPUs and RGB. Currently there are standard desktop-sized ATX motherboards that take 3TB of DDR5, and ATX boards that take 1TB of DDR4 have existed for years.

*if money is not an issue. High end desktop/server platforms often require less cost efficient Registered or Load-Reduced RAM.

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

#99

Post by loxias »

inasio wrote: post #82
loxias wrote: post #76

If only Intel hadn't cancelled Pmem. Insanely high speed, density to match NVMe, could have changed the way we use computers (or at least powered some killer DB servers)

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 persistent storage at the center, surrounded by a ring of compute, for instance.

And weren't we supposed to have memristors by now? ;)

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

#100

Post by kjs3 »

fmajid wrote: post #19

Back when we used something called the DDRdrive X1 as the ZFS ZIL drive (essentially a write log) on our high-performance database machines. It's a PCIe card with 4GB of RAM, 4GB of SLC flash and a supercap so that in the event of a power failure the RAM is written out to flash. https://ddrdrive.com/menu1.html

ZFS was a use case that immediately came to mind.
Post reply on HN