Enterprise SSD / U.2 Recommendation: Spare PCI-E 4.0 16x Port

[scs3jb]

I have a spare PCI-e 4.0 16x slot I'd like to use to put some U.2 drives in.  My motherboard does not support bifurcation.  I'm currently using commercial M2 drives for scratch disks, but I'm killing those pretty fast and have had to RMA them several times.  My aim is to have some high speed cache for downloads and temporary / scratch but with some good endurance rating behind it, then stick these in a ZFS/btrfs array.

 

I've only managed to find a PCI-e 3.0 PEX controllers that will let me get 4x U.2 drives (PCI-e 4.0 bifrucation cards seem to be 10x the price, around 1.3k GBP!):

https://www.aliexpress.com/item/1005005671021299.html?spm=a2g0o.productlist.0.0.16b5a873zNdaEl&mp=1

https://www.aliexpress.com/item/4000029811733.html?spm=2114.12010612.8148356.16.20ee71776HmCGk

 

I was looking at Samsung PM9A3 2.5" U.2 Enterprise SSD/Solid State Drives, but I understand these would run well under the 6GB/s read speeds they should provide, as at PCI-E 3.0 it would be limited to 3.9 GB/s (985MB/s*4) which is nearly 2/3rds the performance. 

 

My questions:

1. Am I overstating the performance drop for PM9A3 if i put them in PCI-e 3.0?
2. If no, is there a high endurance/performance U.2 drive that would be cheaper and better than the PM9A3 (4tb ~ 500 GBP, 2TB ~ 200 GBP) if i'm limited to PCI-e 3.0 speed.
3. Am I doing something stupid and there's a better way to get 4x enterprise flash drives into that PCI-e 4.0 port?

 

Thanks in advance

Edited December 17, 2023 by scs3jb

[tjb_altf4]

I looked at doing something similar to what you described earlier in the year, but I ended up taking a much simpler route with a pair of 1.6TB PM1735 pcie add in cards, which hit my size and performance targets, for a reasonable price all things considered.

 

This is the ebay listing I bought them from https://www.ebay.com/itm/166082555920

[scs3jb]

I looked but I need four devices unfortunately 😔. I could go down pci-e splitter but would still need bifurcation