3 ms·

I have RAM sticks already lying around, so the cost per GB in this scenerio would be zero. Also, I presume that a SATA interface to store data in RAM might have

I have RAM sticks already lying around, so the cost per GB in this scenerio would be zero. Also, I presume that a SATA interface to store data in RAM might have better performance than the average SSD.

smoldesu 4y ago
It would depend on the controller. Most SATA SSDs are already saturating the max throughput of the interface (~600mb/s iirc), so you might want to look for a PCI-based option instead. Even still, I have a hard time imagining the performance squaring up against a proper NVMe drive. I'm not trying to discourage you or anything, but I think paying $50 for an adapter to run 500gb of RAM slower than a $50 500gb NVMe drive is a bit of a goose chase. Good luck in your search regardless!
- universa1 4y ago
  Transfer speed is not everything, latency for random access is one important factor and also performance with randomly accessing many small files... Something even nvme drives are not that fast with...
  - smoldesu 4y ago
    True! All of that would still depend on the way the memory is being accessed though, and if you really want to maximize the speed at-hand then you'd need a powerful memory controller. Once we get to this stage in the thought-experiment though, I think it makes more sense to install the RAM into a normal system and use a RAM disk to store things in it. It's an interesting question, but I think the circumstances explain why nobody has really commercialized something like this. NVMe will get you 90% of the way for 30% of the price, and it's non-volatile to boot.
  - thfuran 4y ago
    But nvme has lower latency than SATA. A ram disk over SATA just doesn't make sense.
kkielhofner 4y ago
RAM requires constant power. If you lose power, you lose data (more-or-less instantly). Not only would you need some kind of controller device to present the RAM as storage to the OS (abstracted NVMe, SATA, something), you would need to figure out how to supply absolutely consistent 100% power to the RAM modules. Such a device would need it's own battery, capacitor, something to continually power the RAM modules. This isn't without precedence - many hardware RAID/storage controllers have aggressive battery-backed caching to persist cache data in the event of power failure. I'm going to go out on a limb and say the approach you're considering is practically infeasible OR (best case) would need an oddball/bespoke device to pull this off. I'm not aware of such a device. Closest you could get is using tmpfs or similar on RAM in RAM slots but it kind of sounds like your existing RAM is electrically/physically incompatible with the system you're attempting this approach with.
- simplotek 4y ago
  > RAM requires constant power. If you lose power, you lose data (more-or-less instantly). It's perfectly fine for some uses, mine included. > I'm going to go out on a limb and say the approach you're considering is practically infeasible. To each his own, but I know for a fact that hardware RAM drives were indeed sold in the past, and after posting this Ask HN I've stumbled upon companies marketing them. https://ddramdisk.store/2023/01/19/the-ddr4-pcie-x8-lady-has-come-out/ https://ddramdisk.store/2023/01/19/the-ddr4-pcie-x8-lady-has...
  - kkielhofner 4y ago
    Yep, can definitely make sense for some applications but important to callout explicitly. Yes! I saw that device from elsewhere in the thread. Wondering when it will be available and what use will look like. Also curious about the battery backup and what maintenance looks like on that.
alexvoda 4y ago
Modern SSDs far exceed the capabilities of SATA. That is why SSDs now use NVME with M.2 or U.3. There exist old slow PCI (DDR1 era) cards that do exactly what you expect: https://www.youtube.com/watch?v=bYbCYgYZVT8 https://www.youtube.com/watch?v=bYbCYgYZVT8 There are also some niche contemporary options: https://ddramdisk.store/2022/05/12/meet-the-latest-release/ https://ddramdisk.store/2022/05/12/meet-the-latest-release/ And in the future there will be very fast options: https://www.anandtech.com/show/16670/using-a-pcie-slot-to-install-dram-new-samsung-cxlmem-expansion-module https://www.anandtech.com/show/16670/using-a-pcie-slot-to-in...
ianburrell 4y ago
You would be wrong about SATA being faster than SSD. Which is why fast SSDs use NVMe. Also, SSDs are much larger and cheaper than RAM. 1TB RAM is still expensive, 1TB SSD is $60. RAM storage has been tried before but was done as PCIe expansion card. It didn’t catch on cause of special drivers, but it only made sense back before NVMe and SSDs were expensive.
- simplotek 4y ago
  > You would be wrong about SATA being faster than SSD. SATA is the computer bus interface, while SSD is the generic name for a storage device that more often than not comes with SATA interfaces. SATA was not a hard requirement, just the one that I felt was the most popular. > Also, SSDs are much larger and cheaper than RAM. SSDs are not cheaper per GB if you already have RAM sticks lying around. Nevertheless this is besides the point, if the goal is to have low latency temp storage when you already maxed out on RAM.
  - ianburrell 4y ago
    Unfortunately, NVMe SSD make RAM drives pointless. SSD, and any RAM drive, saturate SATA. NVMe make SSD perform well but won’t work for RAM drive since it is just a card. PCIe works, the old ones used it. The PCIe RAM drive cards were enterprise and super expensive. You could buy a whole computer for one. It is probably cheaper to sell the RAM sticks and buy SSD. As I mentioned, they are super cheap now and cache would only need small one. Also, setting up RAM drive is a pain. The old cards required special drivers; new ones could probably emulate NVMe. But setting up cache drive and getting programs to use it for temporary storage is annoying. All SSD is easier. There is a lot of experience with using SSD as durable write cache and not as much using disposable temp space. For those who need speed, buying more RAM is a better way of doing it. If you really need speed, then new computer with more RAM and NVMe is better approach. In any case, PCIe RAM drives aren’t made anymore. They were a niche at the time and now there is no market at all.

smoldesu 4y ago

It would depend on the controller. Most SATA SSDs are already saturating the max throughput of the interface (~600mb/s iirc), so you might want to look for a PCI-based option instead. Even still, I have a hard time imagining the performance squaring up against a proper NVMe drive. I'm not trying to discourage you or anything, but I think paying $50 for an adapter to run 500gb of RAM slower than a $50 500gb NVMe drive is a bit of a goose chase. Good luck in your search regardless!

universa1 4y ago
Transfer speed is not everything, latency for random access is one important factor and also performance with randomly accessing many small files... Something even nvme drives are not that fast with...
- smoldesu 4y ago
  True! All of that would still depend on the way the memory is being accessed though, and if you really want to maximize the speed at-hand then you'd need a powerful memory controller. Once we get to this stage in the thought-experiment though, I think it makes more sense to install the RAM into a normal system and use a RAM disk to store things in it. It's an interesting question, but I think the circumstances explain why nobody has really commercialized something like this. NVMe will get you 90% of the way for 30% of the price, and it's non-volatile to boot.
- thfuran 4y ago
  But nvme has lower latency than SATA. A ram disk over SATA just doesn't make sense.

kkielhofner 4y ago

RAM requires constant power. If you lose power, you lose data (more-or-less instantly). Not only would you need some kind of controller device to present the RAM as storage to the OS (abstracted NVMe, SATA, something), you would need to figure out how to supply absolutely consistent 100% power to the RAM modules. Such a device would need it's own battery, capacitor, something to continually power the RAM modules. This isn't without precedence - many hardware RAID/storage controllers have aggressive battery-backed caching to persist cache data in the event of power failure. I'm going to go out on a limb and say the approach you're considering is practically infeasible OR (best case) would need an oddball/bespoke device to pull this off. I'm not aware of such a device. Closest you could get is using tmpfs or similar on RAM in RAM slots but it kind of sounds like your existing RAM is electrically/physically incompatible with the system you're attempting this approach with.

simplotek 4y ago
> RAM requires constant power. If you lose power, you lose data (more-or-less instantly). It's perfectly fine for some uses, mine included. > I'm going to go out on a limb and say the approach you're considering is practically infeasible. To each his own, but I know for a fact that hardware RAM drives were indeed sold in the past, and after posting this Ask HN I've stumbled upon companies marketing them. https://ddramdisk.store/2023/01/19/the-ddr4-pcie-x8-lady-has-come-out/ https://ddramdisk.store/2023/01/19/the-ddr4-pcie-x8-lady-has...
- kkielhofner 4y ago
  Yep, can definitely make sense for some applications but important to callout explicitly. Yes! I saw that device from elsewhere in the thread. Wondering when it will be available and what use will look like. Also curious about the battery backup and what maintenance looks like on that.

alexvoda 4y ago

Modern SSDs far exceed the capabilities of SATA. That is why SSDs now use NVME with M.2 or U.3. There exist old slow PCI (DDR1 era) cards that do exactly what you expect: https://www.youtube.com/watch?v=bYbCYgYZVT8 https://www.youtube.com/watch?v=bYbCYgYZVT8 There are also some niche contemporary options: https://ddramdisk.store/2022/05/12/meet-the-latest-release/ https://ddramdisk.store/2022/05/12/meet-the-latest-release/ And in the future there will be very fast options: https://www.anandtech.com/show/16670/using-a-pcie-slot-to-install-dram-new-samsung-cxlmem-expansion-module https://www.anandtech.com/show/16670/using-a-pcie-slot-to-in...

ianburrell 4y ago

You would be wrong about SATA being faster than SSD. Which is why fast SSDs use NVMe. Also, SSDs are much larger and cheaper than RAM. 1TB RAM is still expensive, 1TB SSD is $60. RAM storage has been tried before but was done as PCIe expansion card. It didn’t catch on cause of special drivers, but it only made sense back before NVMe and SSDs were expensive.

simplotek 4y ago
> You would be wrong about SATA being faster than SSD. SATA is the computer bus interface, while SSD is the generic name for a storage device that more often than not comes with SATA interfaces. SATA was not a hard requirement, just the one that I felt was the most popular. > Also, SSDs are much larger and cheaper than RAM. SSDs are not cheaper per GB if you already have RAM sticks lying around. Nevertheless this is besides the point, if the goal is to have low latency temp storage when you already maxed out on RAM.
- ianburrell 4y ago
  Unfortunately, NVMe SSD make RAM drives pointless. SSD, and any RAM drive, saturate SATA. NVMe make SSD perform well but won’t work for RAM drive since it is just a card. PCIe works, the old ones used it. The PCIe RAM drive cards were enterprise and super expensive. You could buy a whole computer for one. It is probably cheaper to sell the RAM sticks and buy SSD. As I mentioned, they are super cheap now and cache would only need small one. Also, setting up RAM drive is a pain. The old cards required special drivers; new ones could probably emulate NVMe. But setting up cache drive and getting programs to use it for temporary storage is annoying. All SSD is easier. There is a lot of experience with using SSD as durable write cache and not as much using disposable temp space. For those who need speed, buying more RAM is a better way of doing it. If you really need speed, then new computer with more RAM and NVMe is better approach. In any case, PCIe RAM drives aren’t made anymore. They were a niche at the time and now there is no market at all.