Linkreal Pcie 3.0X8 4x M.2 Adapter faster then it should be????

[Oedzesg]

Dear Truenas users,

Today I received my Linkreal adapter from Aliexpress.. link to Ali
Normally I hate Ali for no reason but since my supermicro x12sth-ln4f doesn't support bifurcation I had to look for something with a PLX8747 chip for example.

Installation was easy and TrueNAS instantly saw all 4 nvme drives I had placed in it.

I'm as excited as possible, quickly creating 2 pools with an smb share to test.

What I've done:

Adapter filled with 4 samsung nvme 980 PRO 1tb.

Card installed in a pcie 4.0 x16 slot.

Created 2 mirrored pools and connected via SMB in windows.

Then copied a test file of 10gb and quite a few other large files back and forth so that the ARC would fill properly.

In Windows I get to see that the speed with which the file is transferred from one pool to another is actually faster than my expectation and what the card should be able to do !!


The card is a PCIE 3.0x8
i expected that the 4 nvme cards would be split into 2x2x2x2 which would mean a maximum speed of 1970 MB/s.

In Windows this could be a maximum of 1.97 GB/s.

To my surprise, the speed is 2.28 GB/s!

 

[jgreco]

i expected that the 4 nvme cards would be split into 2x2x2x2

That's not how a PLX chip works; you expected wrong (sorry).

A PLX is a PCIe switch chip, like an ethernet switch, and can route capacity as needed. In this case, each M.2 should be getting a full x4, except that there is a performance penalty for traversing the PLX, so you probably won't get the full speed you would get with a plain ol' M.2-to-PCIe adapter.

 

[Oedzesg]

A PLX is a PCIe switch chip, like an ethernet switch, and can route capacity as needed. In this case, each M.2 should be getting a full x4, except that there is a performance penalty for traversing the PLX,

unbelievable you are right!

Of course I tested from 2 pools on the same card.

I have now also tested from an SSD pool and the speeds are now flying to 3.2 GB/s.

I think the limitation here is the upload of the SSDs.

so you probably won't get the full speed you would get with a plain ol' M.2-to-PCIe adapter.

You are absolutely right here as it is a 3.0 card mounted in a 4.0 slot.



I am happy that I can now make optimal use of my 10 gbe network connection. I have two 10 gbe ports and now even can Consider LACP bond.

 

[Etorix]

unbelievable you are right!

Hope you were ironic here…

I am happy that I can now make optimal use of my 10 gbe network connection. I have two 10 gbe ports and now even can Consider LACP bond.

Mind that this will only be of use to serve multiple clients. The traffic to any single single client will always use one physical link only, so LACC on two 10 GbE does NOT equate to a "20 GbE link".