Sorry for the late reply !
Here's a combination of answers to all the above:
PC motherboard: MSI MEG Z390 ACE Bundkort - Intel Z390 - Intel LGA1151 socket - DDR4 RAM - ATX - 2 x PCI-Express x16, Dual DDR4-2666 - 4 x DIMM slots, 6 x SATA-600 / 3 x M.2 NVMe (2242 / 2260 / 2280), USB 3.1 Type A & C, KillerNIC E2500 Gigabit LAN, Intel 9560 Wireless 802.11ac / Bluetooth 5, Realtek ALC1220 HD Audio (8-kanaler), supports SLI / CrossFireX
CPU: Intel Core i9-9900K Coffee Lake S CPU - 8 core 3.6 GHz - Intel LGA1151 - Processor (CPU), 3.6 GHz (5 GHz Turbo), Unlocked (can be overclocked), 8 core (Octa Core), 16 threads, 16 MB cache, supports Dual Channel DDR4-2666 RAM, 16 PCI Express Lanes, LGA1151 Socket, built in Intel Graphics UHD 630 - 1200 MHz, 95 watt TDP - Coffee Lake S
RAM: Corsair Vengeance LPX DDR4-3200 C16 WH QC - 32GB: 4 x 8 GB (Quad Channel), DIMM 288-pin, DDR4, 3200 MHz / PC4-25600, CL15-15-15-36, 1.35 V, not buffered, no-parity - Corsair Vengeance LPX series
GPU: GIGABYTE GeForce RTX 2080 AORUS Xtreme - 8GB GDDR6 RAM - Overclocked (Core clock 1545 MHz / Boost clock 1890 MHz), 2944 CUDA cores, 8 GB GDDR6 (Memory clock 14 GHz) - 256-bit, PCI Express 3.0 x16, 3 x HDMI 2.0b / 3 x DisplayPort 1.4 / 1 x USB Type C tilslutninger, supports NVIDIA G-Sync, 2 x 8-pins power - Gigabyte WindForce 3X low noise cooler
Storage: 2 x Samsung 970 EVO SSD M.2 2280 - 1TB - SSD (Solid state drive), 1 TB, internal, Speed: 3400 MBps (read) / 2500 MBps (write), IOPS: 500000 (read) / 450000 (write), 1GB LPDDR4 cache, M.2 2280 (80mm), M.2 2280 (80mm), PCI-Express 3.0 x4 NVMe 1.2 (Non-Volatile Memory Express), 256-bit AES kryptering, TCG Opal Encryption - Samsung Phoenix Controller
As mentioned, the storage is split as A ) system & programs and B ) recording from vMix which is also setup as my Dropbox folder, så recordings are synced to other computers for editing afterwards.
@shaneiwarp: I'm using the "high input" and "high output", yes.
@mjgraves: RTX 2080 gpu is in PCI slot 1 (PCI_e1 3.0 x 16) as suggested by MSI and BlackMagic Quad 2 capture card is in slot 6 (PCI_e6 3.0 x4).
@sinc747: I get the "CPU overload" warning
@ThommiTechnik: The write speed of the m.2's are (as you can see more in details above) 2.500 mbps write speed which should be able to record 2500/6000 = 4 streams in your example. I think you would have to build a pretty crazy raid 0 solution to match that and I get the bottleneck / "CPU warnings" even when NOT doing multi-recording - perhaps also see the reply from @rajko, as he's even doing only hdd (not ssd, not raid) without the same limitations as well as the setup, @Peter1000 is describing with a 6 year old i7 setup ... and mine is a superfast PC, way beyond the performance of those two. QUESTION: would a storage-related issue (ie. specific drive / unit too slow) be shown as CPU overload?
Is there somehow for me to compare the benchmarks of this setup to other SIMILAR setups, to see if mine is under-performing - I have this feeling of battling an "invisible ghost" as I'm not even sure where the bottleneck is compared to what I should actually expect in terms of performance?