Optimizing system for Samsung 950 Pro M.2

[Silma]

Hi,

I bought the Samsung 950 Pro M.2 SSD but I don't get the best results, because the M.2 port of my Asus Z97-A motherboard only works as PCIE 2.0 x2.

Ideally, the Samsung SSD needs a PCIE 3.0 x4, so I get 1/4 of the performance I could have.

I've looked at many possibilities and came to the conclusion that the best possibility for me is to purchase a PCIE 3.0 x4 to M.2 adapter such as this.

This would mean my 2 PCIE 3.0 x16 ports would transform from 1 PCIE 3.0 x16 card + 2nd PCIE 3.0 16 unavailable into 2 PCIE 3.0 x8 ports.

According to the tests I've seen, an NVIDIA GTX970 graphic card, which is what I have, won't suffer in the performance department by going x8 instead of x16.

- If anybody has tests that prove it's false, please send me the links.
- Now my question is, will this work ? E.g. Can I put a PCIE 3.0 x4 card in a PCIE 3.0 x16 port running at x8 or won't it work?
- Any other suggestions ?

Thanks,
Silma

 

[mv2devnull]

Can I put a PCIE 3.0 x4 card in a PCIE 3.0 x16 port running at x8?

Yes.
First, even though a physical connection slot is xN, the electrics may be less. (E.g. There are "x4" slots that have only "x1" lanes.) A x4 card fits nicely into x16 slot.

Second, both the board and the card negotiate on how many lanes are used. The SLI graphics is an example. The motherboard disables half of the lanes of the first x16 slots and the GTX970
complies by using only its first eight lanes. Similarly, the motherboard will use only 4 lanes (of 8) to communicate with that x4 card.

 

[Silma]

Thanks!

I ordered a card and will get it next week. I'll update this post after the install

 

[Silma]

I installed the Pcie 3.0 x4 -> M.2 card in the computer.

I am happy to report the Samsung Magician benchmarks have greatly improved over my motherboard's Pcie 2 x2 M.2 slot:

2 254 MB/s sequential reads vs 834 before
1 530 MB/s sequential writes vs 807 before

However, I am disappointed by the IOPS

157 767 Read IOPS vs 158 870 IOPS before
63 452 write IOPS vs 64 770 after

Also, my Crucial M500 SSD destroys the Samsung 950 M.2 Pro in Write IOPS:
80 054 write IOPS vs 63 452 for the Samsung.

I am not sure how IOPS translates for PC/workstation usage, but it seems the increased bandwidth is not the limiting factor for flash storage IOPS today.

 

[Hellhammer]

Are you running the latest Samsung NVMe driver? The early versions had some issues with low random write IOPS, but that's fixed in the current version.