I'm surprised we haven't seen a smaller than M.2 form factor for SATA on embedded devices. It seems like the big limiter on devices like the Raspberry Pi and others are the sd cards/emmc modules, since the amount processing power and ram have been continually going up.
If you need disk performance on the Pi 4, wouldn't it make more sense to only keep the kernel,initrd on the sdcard and mount the primary filesystem off a USB3 device (like an mSATA-2-USB enclosure), that is if you have the space to spare for it in your project/enclosure?
I did something similar with one of the SolidRun devices, but I had to scuttle it due to other hardware problems:
If you need disk performance on the Pi 4, wouldn't it make more sense to only keep the kernel,initrd on the sdcard and mount the primary filesystem off a USB3 device (like an mSATA-2-USB enclosure), that is if you have the space to spare for it in your project/enclosure?
I did something similar with one of the SolidRun devices, but I had to scuttle it due to other hardware problems:
https://penguindreams.org/blog/review-clearfog-pro/