4 ms·

When I say "old RAM" I mean from the same, current, modern era, though, yes, it is often smaller or lower-density due to being pulls from upgrades, for example.

by mmt 8y ago

When I say "old RAM" I mean from the same, current, modern era, though, yes, it is often smaller or lower-density due to being pulls from upgrades, for example. The modern era often also includes previous-generation technology, such as DDR3 in use today even though DDR4 is available (with non-intuitive pricing relationships at any given time). That said, why would size (density) have to do with being economical? Are the required memory controllers to expensive, because there simply aren't any other than inside CPUs? The train of logic needs explaining.

bhouston 8y ago
It is hard to recycle used equipment at scale generally and economically. Old ram if it is small will take up a ton of space as well. It is the same reason why I don't reuse old hds, it does make economic sense. I would rather overpay for a 12 tb drive than get 12 1tb drives for free. The trouble, increased failure rates, the space usage etc is just not worth it. A few ssds in a high speed non redundant raid would be much better. Or a new class of volitile slow ram that has tons of space would be interesting. So more space at lower cost than ram but slower. That would be interesting. Give me a few 128GB sticks please.
- mmt 8y ago
  > It is hard to recycle used equipment at scale generally and economically. Old ram if it is small will take up a ton of space as well. You've said this already, but both of these statements need unpacking and quantifying, especially "a ton of space". There's been a persistent myth that, in datacenters, it's space that's the expensive and/or scarce resource. It isn't. It's power and cooling. Only in the last 5-6 years have we seen the construction of datacenter facilities that could handle half-U densities, let alone what some "blade" systems were trying to do. > It is the same reason why I don't reuse old hds, it does make economic sense. I would rather overpay for a 12 tb drive than get 12 1tb drives for free. The trouble, increased failure rates, This is a false equivalence, since RAM doesn't have moving parts. A better comparison would be if you discovered a box of brand new drives, still sealed in their bags with dessicant. Even ignoring the fact that 12 drives will have much better performance than a single one, would you still just blindly throw them away to buy the single one, without considering if it would be cheaper to buy 12 disk slots instead? If the answer is "yes", this is inconsistent with "economic". > the space usage etc is just not worth it. I've already addressed the space usage as a red herring. What's the "etc"? > A few ssds in a high speed non redundant raid would be much better. Why a few? Isn't a single high-end one enough to saturate an NVMe or PCIe slot these days? > Or a new class of volitile slow ram that has tons of space would be interesting. So more space at lower cost than ram but slower. That would be interesting. Give me a few 128GB sticks please. What if this "new" class is actually DDR3 and the "sticks" are actually PCIe cards? That's what I've been suggesting.
  - bhouston 8y ago
    > Even ignoring the fact that 12 drives will have much better performance than a single one, would you still just blindly throw them away to buy the single one, without considering if it would be cheaper to buy 12 disk slots instead? Density does matter. And 12 individual disk will have a high failure rate than one disk because there is 12x electronics, 12x motors, 12x seals. Also the power needs for 12 disks is higher than 1. And you would need more raid cpu power to coordinate 12x disks. > Why a few? Isn't a single high-end one enough to saturate an NVMe or PCIe slot these days? Sure. I feel like you are just arguing for arguing sake here. You get 1GBps from most ssds and ddr3 is around 15GBps or so. > What if this "new" class is actually DDR3 and the "sticks" are actually PCIe cards? That's what I've been suggesting If it was significantly cheaper and new sure. Ddr3 is just as expensive as ddr4 right now. No body running a professional data center wants the unpredictability of used parts unless they have had very consistent and tame histories. According to large scale studies ddr has increasing error rates as they age: https://ai.google/research/pubs/pub35162 https://ai.google/research/pubs/pub35162
    - Dylan16807 8y ago
      > Density does matter. And 12 individual disk will have a high failure rate than one disk because there is 12x electronics, 12x motors, 12x seals. If you absolutely have to store 12TB of data and not spend another dollar, more drives are less reliable. In most situations having more drives makes it a lot easier to protect your data, because you can use parity. > And you would need more raid cpu power to coordinate 12x disks. A very small CPU cost; the drives are only doing 100 IOPS. And in return you get 4x-10x the throughput.
      - mmt 8y ago
        > If you absolutely have to store 12TB of data and not spend another dollar, more drives are less reliable. In most situations having more drives makes it a lot easier to protect your data, because you can use parity. I think what we're talking about is aggregates, so think about 120 1TB drives versus 10 12TB drives, if that's helpful. If the failure rate per drive is comparable, then the failure rate per TB is 12 times higher for the the smaller drives. Arranging them in a RAID doesn't change this calculation. > A very small CPU cost; the drives are only doing 100 IOPS. And in return you get 4x-10x the throughput. I did stipulate to ignoring any performance difference, so we can assume that those 12 drives are concatenated rather than RAIDed, which I believe is an immesurable amount of difference in CPU load.

by mmt 8y ago

bhouston 8y ago

It is hard to recycle used equipment at scale generally and economically. Old ram if it is small will take up a ton of space as well. It is the same reason why I don't reuse old hds, it does make economic sense. I would rather overpay for a 12 tb drive than get 12 1tb drives for free. The trouble, increased failure rates, the space usage etc is just not worth it. A few ssds in a high speed non redundant raid would be much better. Or a new class of volitile slow ram that has tons of space would be interesting. So more space at lower cost than ram but slower. That would be interesting. Give me a few 128GB sticks please.

mmt 8y ago
> It is hard to recycle used equipment at scale generally and economically. Old ram if it is small will take up a ton of space as well. You've said this already, but both of these statements need unpacking and quantifying, especially "a ton of space". There's been a persistent myth that, in datacenters, it's space that's the expensive and/or scarce resource. It isn't. It's power and cooling. Only in the last 5-6 years have we seen the construction of datacenter facilities that could handle half-U densities, let alone what some "blade" systems were trying to do. > It is the same reason why I don't reuse old hds, it does make economic sense. I would rather overpay for a 12 tb drive than get 12 1tb drives for free. The trouble, increased failure rates, This is a false equivalence, since RAM doesn't have moving parts. A better comparison would be if you discovered a box of brand new drives, still sealed in their bags with dessicant. Even ignoring the fact that 12 drives will have much better performance than a single one, would you still just blindly throw them away to buy the single one, without considering if it would be cheaper to buy 12 disk slots instead? If the answer is "yes", this is inconsistent with "economic". > the space usage etc is just not worth it. I've already addressed the space usage as a red herring. What's the "etc"? > A few ssds in a high speed non redundant raid would be much better. Why a few? Isn't a single high-end one enough to saturate an NVMe or PCIe slot these days? > Or a new class of volitile slow ram that has tons of space would be interesting. So more space at lower cost than ram but slower. That would be interesting. Give me a few 128GB sticks please. What if this "new" class is actually DDR3 and the "sticks" are actually PCIe cards? That's what I've been suggesting.
- bhouston 8y ago
  > Even ignoring the fact that 12 drives will have much better performance than a single one, would you still just blindly throw them away to buy the single one, without considering if it would be cheaper to buy 12 disk slots instead? Density does matter. And 12 individual disk will have a high failure rate than one disk because there is 12x electronics, 12x motors, 12x seals. Also the power needs for 12 disks is higher than 1. And you would need more raid cpu power to coordinate 12x disks. > Why a few? Isn't a single high-end one enough to saturate an NVMe or PCIe slot these days? Sure. I feel like you are just arguing for arguing sake here. You get 1GBps from most ssds and ddr3 is around 15GBps or so. > What if this "new" class is actually DDR3 and the "sticks" are actually PCIe cards? That's what I've been suggesting If it was significantly cheaper and new sure. Ddr3 is just as expensive as ddr4 right now. No body running a professional data center wants the unpredictability of used parts unless they have had very consistent and tame histories. According to large scale studies ddr has increasing error rates as they age: https://ai.google/research/pubs/pub35162 https://ai.google/research/pubs/pub35162
  - Dylan16807 8y ago
    > Density does matter. And 12 individual disk will have a high failure rate than one disk because there is 12x electronics, 12x motors, 12x seals. If you absolutely have to store 12TB of data and not spend another dollar, more drives are less reliable. In most situations having more drives makes it a lot easier to protect your data, because you can use parity. > And you would need more raid cpu power to coordinate 12x disks. A very small CPU cost; the drives are only doing 100 IOPS. And in return you get 4x-10x the throughput.
    - mmt 8y ago
      > If you absolutely have to store 12TB of data and not spend another dollar, more drives are less reliable. In most situations having more drives makes it a lot easier to protect your data, because you can use parity. I think what we're talking about is aggregates, so think about 120 1TB drives versus 10 12TB drives, if that's helpful. If the failure rate per drive is comparable, then the failure rate per TB is 12 times higher for the the smaller drives. Arranging them in a RAID doesn't change this calculation. > A very small CPU cost; the drives are only doing 100 IOPS. And in return you get 4x-10x the throughput. I did stipulate to ignoring any performance difference, so we can assume that those 12 drives are concatenated rather than RAIDed, which I believe is an immesurable amount of difference in CPU load.