M.2 SSD Samsung to Motherboard. Fullspeed?

[MaxJTihomirov]

Hey! My set is 9900KS+Radeon VII+AsRock SteelLegend Z390
Catalina 10.15.2

I've got 2 m.2 sockets on my motherboard and i plug in SSD M.2 Samsung EVO 970+ in each and made RAID 0.
But i think speed of it is too slow

Each as i know should have the same speed

Can anybody tell me whats wrong? Should i buy PCI-M.2 card for fullspeed?




And this is separate speed

as you see the same as in RAID 0

 

[jaymonkey]

My set is 9900KS+Radeon VII+AsRock SteelLegend Z390. I've got 2 m.2 sockets on my motherboard and i plug in SSD M.2 Samsung EVO 970+ in each and made RAID 0. But i think speed of it is too slow

@MaxJTihomirov,

Your M.2 ports will most likely be served by the PCH, so the M.2 Raid will be limited to the DMVI V3 PCH to CPU interconnect (equivalent to PCIe Gen 3 at x4 Lanes) which is shared with all the other devices routed through the PCH (Ethernet, All USB ports, All SATA Ports, on-board audio ..etc)

The only way to get the full native speed of 2 x M.2 SSD's in RAID 0 would be to use a PCIe adapter(s) so that the M.2 SSD's are directly linked to the CPU.

However Intel Desktop Class CPU's only have 16 CPU lanes available so if you did this, it would cause your GPU to drop from x16 lanes to x8 lanes. The effect of this is not so bad in most instances (a loss of around 5% in performance), but if you have anything else on the PCIe bus then it would drop the GPU to x4 lanes which a AMD GPU can use but the performance hit is much more noticeable than x8 lanes.

Cheers
Jay

 

[MaxJTihomirov]

@MaxJTihomirov,

Your M.2 ports will most likely be served by the PCH, so the M.2 Raid will be limited to the DMVI V3 PCH to CPU interconnect (equivalent to PCIe Gen 3 at x4 Lanes) which is shared with all the other devices routed through the PCH (Ethernet, All USB ports, All SATA Ports, on-board audio ..etc)

The only way to get the full native speed of 2 x M.2 SSD's in RAID 0 would be to use a PCIe adapter(s) so that the M.2 SSD's are directly linked to the CPU.

However Intel Desktop Class CPU's only have 16 CPU lanes available so if you did this, it would cause your GPU to drop from x16 lanes to x8 lanes. The effect of this is not so bad in most instances (a loss of around 5% in performance), but if you have anything else on the PCIe bus then it would drop the GPU to x4 lanes which a AMD GPU can use but the performance hit is much more noticeable than x8 lanes.

Cheers
Jay

As i thought! Thank you so much!!! Anyway i wanted to buy something like SSD ASRock ULTRA QUAD M.2 CARD x4
You are the best!

 

[MaxJTihomirov]

@MaxJTihomirov,

Your M.2 ports will most likely be served by the PCH, so the M.2 Raid will be limited to the DMVI V3 PCH to CPU interconnect (equivalent to PCIe Gen 3 at x4 Lanes) which is shared with all the other devices routed through the PCH (Ethernet, All USB ports, All SATA Ports, on-board audio ..etc)

The only way to get the full native speed of 2 x M.2 SSD's in RAID 0 would be to use a PCIe adapter(s) so that the M.2 SSD's are directly linked to the CPU.

However Intel Desktop Class CPU's only have 16 CPU lanes available so if you did this, it would cause your GPU to drop from x16 lanes to x8 lanes. The effect of this is not so bad in most instances (a loss of around 5% in performance), but if you have anything else on the PCIe bus then it would drop the GPU to x4 lanes which a AMD GPU can use but the performance hit is much more noticeable than x8 lanes.

Cheers
Jay

So if i'll use pci-e card and my radeon VII i get -5% power of videocard and fullspeed SSD RAID right?

 

[jaymonkey]

i wanted to buy something like SSD ASRock ULTRA QUAD M.2 CARD x4

@MaxJTihomirov,

Theoretically if you populated all four M.2 ports on the ASRock ULTRA QUAD M.2 CARD x4 then it would use all 16 CPU PCIe lanes (4 x 4), and your GPU would not work. If you only use the first two M.2 ports and put it in a PCIe slot that only has x8 lanes (must be configured as 2 x 4) then it would leave x8 lanes for your Radeon VII.

In most instances running a GPU at x8 PCIe lanes as opposed to the full x16 lanes only results in a slight performance loss, usually no more than 5%. There are very few apps that can saturate the full PCIe V3 bandwidth when running a GPU at x16 lanes.

Important: Check your motherboard to see if it supports a CPU PCIe lane allocation of 2 x 4 or 4 x 4 on a specific slot. On newer motherboards there is sometimes a feature in the BIOS called Bifurcation which allows for separation of PCIe lanes.

If your motherboard does not support either of the above features then the chances are you will only be able to use the first M.2 port on the ASRock ULTRA QUAD M.2 CARD x4 card.

Most simple 4 x M.2 carrier cards (like the ASRock ULTRA QUAD M.2) only work on X299 motherboards as Xeon CPU's have many more CPU PCIe lanes available and can easily accommodate something like this (also on some newer AMD motherboards). Check that it's going to work with your motherboard before committing to purchase it, my gut instinct tells me that it wont work but i could be wrong, it all depends on how configurable the PCIe bus is on your motherboard.

Intel Desktop class CPU's are severely hampered by only having 16 CPU PCIe lanes, in this age of cheap, high capacity and fast M.2 NVMe SSD's it's high time Intel pulled its finger out and gave the Desktop class CPU's at least 24 PCIe lanes.

Unfortunately Intel is very stuck in its ways and deliberately keeps the desktop class CPU's PCIe limited in order to force power users on to the more expensive X299 platform for which they have always charged a premium for. AMD has upset that market with its ThreadRipper CPU's which has forced Intel to lower the cost of the latest 10th gen X299 CPU's to almost half the price of what the 8th and 9th gen X299 CPU's cost.

Even the new AMD Ryzen AM4 desktop platform has 16 + 4 CPU lanes in addition to being PCIe V4 which allows manufactures to produce motherboards with better M.2 support.

Cheers
Jay