Identical NVME SSD's but one is way slower


So recently a friend and I built a PC since we wanted to give Chia farming a try. Our setup consists of the following components:

  • MSI Z590 A PRO motherboard
  • 2x 16GB Corsair DDR4-3200 RAM
  • 2x Samsung 980 NVME M.2 SSD’s
  • 3x 6TB Hard drives
  • Intel Core i7-10700KF

We use the Ubuntu OS.

We played around a bit with the settings and managed to get a plotting speed of around 7.5 hours with 4 threads per plot and 6000 MiB ram assigned.

However, recently we noticed that one of the SSD’s is lagging behind… We run 2 plots in “true” parallel (1 on each SSD) and then stagger multiple plots with a delay time according to the time it takes for Phase 1 to complete. During the initial tests, the plotting speeds were rougly the same on both SSD’s. Now, however, we see that one of them consistently has a significant increase in time it takes for all phases to complete.

To give you an example:

SSD1 phase 1 completion time approx. 10.000 seconds

SSD2 phase 1 completion time approx. 38.000 seconds

I’m not very technical so I have no idea what could be wrong… Taking a look at glances in the terminal reveals that one of the SSD’s has a pretty consistent writing speed hovering around 35 M/s. The other SSD has a writing speed ranging from 0-250 M/s.

Does anybody know what could cause this difference? No settings were changed, at least not to my knowledge. Thanks!

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Those are horrible SSDs to plot on, maybe one ran out of cache before the other, but even running a single plot on them is going to be painfully slow after a while. Check here to find out a bit more.


Ahh thanks! I had no clue. I wish I had seen your video before buying all the components. We tried to keep it on a budget while still looking at reading/writing speeds and TBW, but I guess we chose wrong.

Looking at the individual drives, they both have about an equal amount of read/written data and nothing special that stands out and differs.

Do your reckon it helps if we put the 2 NVME’s in RAID0? Else I guess we’ll just have to deal with it and look for some other SSD’s in the future. :slight_smile: Thanks for your answer and very informational video!

Ohh another thing! I did just notice that there is quite a difference in temperature of the NVME drives.

“Fast” nvme drive: Sensor 1 temp 42°C, sensor 2 temp 72°C
“Slow” nvme drive: Sensor :-1 temp 55°C, sensor 2 temp 87°C

I’ll shut down everything on the slow NVME drive as this seems way too much…

Some other things to check. Are these nvme ssds both on the motherboard? Are any on a PCI-e card sharing PCI-e lanes? Is one used as a boot drive? Often other add in cards and/or SATA devices degrade speeds of other installed devices. Anything else in slots? I would carefully check your motherboard manual and see if there are any caveats listed around nvme drive limitations. See pages 5-6, 14-16, it can get confusing.

Also check which of your ssds have heatsinks, if any. Consider adding some.

These NVME M.2’s are both on the motherboard. The motherboard has 3 slots (M2_1, _2 and _3) of which only the last 2 can be used with a 10th generation processor. If I’d want to use the _1 slot I’d need a 11th gen processor, but that’s not the case.

The PCIE x16 (the best one according for GPU according to the manual) lane is used for my GPU and this one is right above one of the NVME drives. I shut down all the plots running on the “slow” NVME and the temperature immediately dropped! The one that’s right under the GPU is the one that remains the coolest (possibly due to the GPU fan in it’s vincinity).

I’ll look to buy a heatsink and in the meantime I’ll check if speeding up the system fans is of any help. :slight_smile:

Sensor 2 is the controller and it’s throttling due to high temps which is causing your slowdown. Nothing to do with PCIe bandwidth as plotting rarely (if ever) saturates PCIe with concurrent plots.

Also if you run it headless then you don’t need the GPU at all and it’ll use less power and produce less heat which could be affecting other components.

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