PCIe Slot Splitting in 5810?

@the.mknabster , yes, that is a dual slot Dell OEM.  I like that version better than the Quad Ultra Speed Drive because beside good cooling, it does support the enterprise NVME (the long version 110mm).  Asus Hyper stock would be in and out, but Amazon warehouse in US had them on special around 40 USD, so keep an eye out for them.  Also check out the Cablecc  dual and quad and they had been around 25 to 30 USD, and they have good review on US Amazon.

Thanks for your response Chino! Especially with it so close to the GPU, i do worry about overheating with them. Have you ever heard of the Dell DPWC300 card before? I found one on ebay for a reasonable price and it has a fan, but i can't find much info on it online. I was also looking at the Asus Hyper card which has a fan as well, but finding that one in stock has been problematic.

I probably would opt for a card with a built in fan, like the Asus or Dell, and the best price i can find for them is about $54. So that's doable for me. I just need to find out the dimensions of the Dell card so i can make sure it'll physically fit underneath my GPU, because that thing is a behemoth in the computer (I have a Dell GTX 1070 in there).

Thanks so much for your quick responses, i'm glad all this will work!

@the.mknabster , I would with certain configuration.  I had one setup with enterprise SSD (SM963), so the heat does not affect the endurance (6TB DWPD) as it does when using client SSD.  Also if the system use a single Quadro graphics and the other slots have enough space for airflow.  The front fan (next to HDD cage) moves enough air to keep the NVME cool around 46 - 50 degree.  But I just checked today and the price for Cablecc is double from what it was.  Asus Hyper and Dell also are good choice if you can get them around 50 USD.  

You are doing good right now by doing research and planning, be patient and wait for good price on the items you want.  

Thanks for all information on this post since I am in the similar situation to upgrade T5810, there could be an option for Jeyi ihyper pro versions with aluminum case and fan, for its pcie 3.0 version, it's price is nearly one fourth of Asus M2 hyper from aliexpress. But it is still not right time to buy since price is roaring recently.

For T5810 pcie bifurcation, is it possible to see the options form BIOS or it is automatically recognized once you insert the expansion card?

@Thomas miao , IIRC it was recognized automatically.  You would see all the adapters (with drives) in PCI slots as mass storage.  Once in OS, you can see all your drives, depends on how many adapter and drives you used.

@the.mknabster , they are designed as single slot cards and they will fit next to your GTX 1070.

@Thomas miao yes, you can perform clean install Windows 10 on your NVME drive and it will boot natively (some older machines will required Clover, Refind to boot).  Assuming all your drives are new and unallocated, Windows 10 will list your adapter (with drives) as disk 0, disk 1, and so on, just select the disk (drive) you want, Windows 10 will prep the partition and proceed to installation.

NVME drives can reach 3000 MB/s in Read speed, Windows 10 will load in seconds.  I don't see any advantage in using RAID for your OS.  Save them for data drive, scratch drive, game drive, whereas large data transfer is used frequently.

Don't mean to be rude but we don't want to hijack the thread from OP neither.

thanks A lot，very clear now.

I am pleased to confirm that "ASUS Hyper M.2 x16 Gen 4 Card" works well on Dell T5810. T5810 has PCIe bifurcation, so 4 SSDs can be detected automatically.

For those who is looking for a solution, either the motherboard should have PCIe bifurcation or else you need to buy a PCIe SSD adapter that has a chip on the adapter to perform bifurcation. If you choose a PCIe m.2 SSD adapter with bifurcation chip, then the adapter will be expensive.

Luckily, T5810 has PCIe bifurcation. So, a cheap PCIe m.2 SSD adapter without bifurcation chip will work. ASUS Hyper M.2 x16 Gen 4 Card is a good choice as it's nicely built, easy to get and cost effective.

I see people are saying the T5810 natively supports PCIe bifurcation, could someone clarify how to configure this? I have a PCIE nvme adapter card coming in the mail, but don’t see anything in the bios to configure PCIE bifurcation, and the YouTube video showing how to do so for the T5820 looks different. Does the card need to be installed and populated to show this field?

There is no settings for bifurcation in t5810, just install up to 4 NVMe drives into your adapter and plug it in a x16 slot.  You will see all those drives in Disk Management.  Just that simple.