3 ms·

There should be a benchmark for filling a drive 100%, then doing 4K random writes. I'm pretty sure this would kill any MLC/TLC/QLC drive at a few billion writes

by ece 6y ago

There should be a benchmark for filling a drive 100%, then doing 4K random writes. I'm pretty sure this would kill any MLC/TLC/QLC drive at a few billion writes or less. It wouldn't kill Optane, which would probably remain performant as well, and possibly some SLC drives.

wmf 6y ago
Server/datacenter/enterprise SSDs are benchmarked that way.
gruez 6y ago
If you're talking about performance benchmarks they got that, it's under the "Sustained IO Performance" section. If you're talking about testing to see how fast it breaks, I really don't see the point because that type of workload pretty much never happens in real life, especially for consumer SSDs.
- ece 6y ago
  I think people filling up drives and then making space as needed happens more often than one might think. It's probably most common on phones/tablets, but even I only do remote backups once a partition is 80% or so full, and at times I'll just delete the largest files I've managed to download. I over-provision, but for those that don't over-provision their SSDs, and run them on the fuller side, they might go through the TBW rating quicker than others who don't. This test would measure the quickest such outcome for each SSD.
exmadscientist 6y ago
A similar test has been done: https://techreport.com/review/27909/the-ssd-endurance-experiment-theyre-all-dead/ https://techreport.com/review/27909/the-ssd-endurance-experi... TL;DR: SSDs are harder to kill than they might seem.
- ece 6y ago
  Thanks for the link, it's nice to see such results from 256GB SATA drives (No drive dying before 600TBW, and the 840 PRO going up to 2.4PBW, I have a 850 PRO in a laptop myself), but it would still be interesting to see similar tests for NVMe drives.
- fomine3 6y ago
  I'd like to see similar test on modern 3D NAND SSD. Possibly 3D is not good for many 4K writes due to larger page size?
mgerdts 6y ago
Both this drive and the 980 pro have a dynamic SLC cache. When there is a significant amount of erased space available, they will each sustain about 5000MB/s. This drops to about 2000MB/s as the SLC fills. The 980 pro hits a cliff at about 75% written. The SN850 requires less erased space, but I forget the exact point it cuts out. The size of the dynamic SLC, when available, is roughly 1/3 of the erased space, with an upper bound. If you don't need the capacity, set aside 30% of the drive in a partition you won't use, then use blkdiscard to erase it. Not only will this increase write performance, it may increase endurance. Increasing endurance with these drives is of interest because they are rated at 0.3 DWPD, compared to 1 DWPD with previous generation drives. Taking over-provisioning to an extreme, I found that erasing a 980 Pro, then creating a 100 GB partition allowed me to overwrite that partition many times over at a sustained 5000 MB/s. This could be interesting for journaling, so long as you are ok with lack of power loss protection (unlikely for a journal) or cache flushes could be performed to ensure the data is on NAND, not just in DRAM. But really, if you need to sustain writes at such a high rate, both of these are the wrong drive for endurance reasons. With optane stuck at PCIe gen 3, it may be great for low latency small blocks, but it won't exceed 3500 MB/s in a x4 NVMe form factor.
- ece 6y ago
  Over-provisioning is doable since more 15" laptops and motherboards are starting to have 2 NVMe slots, and you always could've gotten additional PCIe->NVMe slots for a motherboard. If you're still after endurance, low latency and a lot of random writes for journaling or a Bazel compiler cache, it seems like the P4801X is your best bet now, if you've got a 110mm NVMe slot.
- jlgaddis 6y ago
  > If you don't need the capacity, set aside 30% of the drive in a partition you won't use, then use blkdiscard to erase it. I assume this is the recommended method for over-provisioning nowadays? I've no idea where -- as it's been several years ago now -- but I can recall recommendations to use the HPA for this. I have no way to know, for certain, whether it actually helps but that's what I used to do (setting ~25% of the drive aside in the HPA). Anecdotally, I've yet to have such an SSD die on me, although I'm not exactly torturing them either.

by ece 6y ago

wmf 6y ago

Server/datacenter/enterprise SSDs are benchmarked that way.

gruez 6y ago

If you're talking about performance benchmarks they got that, it's under the "Sustained IO Performance" section. If you're talking about testing to see how fast it breaks, I really don't see the point because that type of workload pretty much never happens in real life, especially for consumer SSDs.

ece 6y ago
I think people filling up drives and then making space as needed happens more often than one might think. It's probably most common on phones/tablets, but even I only do remote backups once a partition is 80% or so full, and at times I'll just delete the largest files I've managed to download. I over-provision, but for those that don't over-provision their SSDs, and run them on the fuller side, they might go through the TBW rating quicker than others who don't. This test would measure the quickest such outcome for each SSD.

exmadscientist 6y ago

A similar test has been done: https://techreport.com/review/27909/the-ssd-endurance-experiment-theyre-all-dead/ https://techreport.com/review/27909/the-ssd-endurance-experi... TL;DR: SSDs are harder to kill than they might seem.

ece 6y ago
Thanks for the link, it's nice to see such results from 256GB SATA drives (No drive dying before 600TBW, and the 840 PRO going up to 2.4PBW, I have a 850 PRO in a laptop myself), but it would still be interesting to see similar tests for NVMe drives.
fomine3 6y ago
I'd like to see similar test on modern 3D NAND SSD. Possibly 3D is not good for many 4K writes due to larger page size?

mgerdts 6y ago

Both this drive and the 980 pro have a dynamic SLC cache. When there is a significant amount of erased space available, they will each sustain about 5000MB/s. This drops to about 2000MB/s as the SLC fills. The 980 pro hits a cliff at about 75% written. The SN850 requires less erased space, but I forget the exact point it cuts out. The size of the dynamic SLC, when available, is roughly 1/3 of the erased space, with an upper bound. If you don't need the capacity, set aside 30% of the drive in a partition you won't use, then use blkdiscard to erase it. Not only will this increase write performance, it may increase endurance. Increasing endurance with these drives is of interest because they are rated at 0.3 DWPD, compared to 1 DWPD with previous generation drives. Taking over-provisioning to an extreme, I found that erasing a 980 Pro, then creating a 100 GB partition allowed me to overwrite that partition many times over at a sustained 5000 MB/s. This could be interesting for journaling, so long as you are ok with lack of power loss protection (unlikely for a journal) or cache flushes could be performed to ensure the data is on NAND, not just in DRAM. But really, if you need to sustain writes at such a high rate, both of these are the wrong drive for endurance reasons. With optane stuck at PCIe gen 3, it may be great for low latency small blocks, but it won't exceed 3500 MB/s in a x4 NVMe form factor.

ece 6y ago
Over-provisioning is doable since more 15" laptops and motherboards are starting to have 2 NVMe slots, and you always could've gotten additional PCIe->NVMe slots for a motherboard. If you're still after endurance, low latency and a lot of random writes for journaling or a Bazel compiler cache, it seems like the P4801X is your best bet now, if you've got a 110mm NVMe slot.
jlgaddis 6y ago
> If you don't need the capacity, set aside 30% of the drive in a partition you won't use, then use blkdiscard to erase it. I assume this is the recommended method for over-provisioning nowadays? I've no idea where -- as it's been several years ago now -- but I can recall recommendations to use the HPA for this. I have no way to know, for certain, whether it actually helps but that's what I used to do (setting ~25% of the drive aside in the HPA). Anecdotally, I've yet to have such an SSD die on me, although I'm not exactly torturing them either.