i have rog viii dark hero motherboard and want to use it as a NAS. i have 2 gpu's and a usb expansion card and ethernet card.

how many sata drive can i connect? will a ASUS hyper m.2 drive work? how will a m.2 to oculink adapter benefit me to add more drives using a x4 Pcie lane?

Your ASUS ROG Crosshair VIII Dark Hero is actually a very good base for a DIY NAS because it has a lot of SATA ports and flexible PCIe lanes. Let’s break down what you can realistically connect and how expansion options like Hyper M.2 or OCuLink would work.

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1. Native drives you can connect (without adapters)

Your motherboard provides:

• 8 × SATA 6 Gb/s ports

• 2 × M.2 slots (PCIe 4.0 x4 NVMe or SATA) (@ROG)

So directly on the board you can run:

• 8 SATA drives

• 2 NVMe drives

➡ Total = 10 drives without any add-in cards

Importantly:
Unlike many boards, using both M.2 slots does NOT disable SATA ports on this model. (Tom's Hardware)

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2. PCIe slot layout (important for NAS expansion)

Main slots on this board:

• PCIe 4.0 x16 (CPU) – GPU slot

• PCIe 4.0 x16 (CPU) – runs x8 if both used

• PCIe 4.0 x16 (chipset) – x4 electrical

• PCIe 4.0 x1 slot (@ROG)

If you already have:

• 2 GPUs

• USB expansion card

• Ethernet card

You’re already consuming several slots, which limits expansion options.

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3. Will an ASUS Hyper M.2 card work?

The ASUS Hyper M.2 x16 Card V2 can hold 4 NVMe drives, but it only works properly if the motherboard supports PCIe bifurcation (splitting x16 → x4/x4/x4/x4).

Your board does support bifurcation, but there are caveats:

Best case

If installed in a x16 slot with bifurcation enabled

You can run:

• 4 NVMe drives on one card

If installed in a x8 or x4 slot

Then you get:

• x8 slot → 2 NVMe drives

• x4 slot → 1 NVMe drive

So with two GPUs already occupying the main slots, the Hyper card will likely only run 1–2 drives.

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4. Using an M.2 → OCuLink adapter (very useful for NAS)

This is actually a great NAS trick.

What it does

An M.2 NVMe slot (x4) is converted into OCuLink (SFF-8611).

Then you can connect:

• OCuLink → 4-port SATA

• OCuLink → 8-port SATA

• OCuLink → U.2 / NVMe backplane

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Bandwidth

An M.2 PCIe 4.0 x4 slot ≈ 8 GB/s

Typical SATA drives:

• ~200 MB/s each

So:

• 4 SATA drives ≈ 800 MB/s

• 8 SATA drives ≈ 1.6 GB/s

➡ Even an x4 link easily handles 8 drives

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5. Example NAS configuration with your board

Possible layout:

Motherboard

• 8 SATA drives

M.2 slots

• 2 NVMe cache drives
  or

• 1 NVMe + 1 OCuLink adapter

PCIe x4 slot

• 8-port HBA (LSI card)

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Realistic drive counts

Without crazy mods:

Method	Drives
Motherboard SATA	8
M.2 NVMe	2
OCuLink adapter	4–8
PCIe HBA card	8–16

Total possible: 20–30 drives

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6. Best NAS expansion method (recommended)

Instead of Hyper M.2, I strongly recommend:

PCIe SAS HBA

Examples:

• LSI 9211‑8i

• LSI 9300‑8i

Advantages:

• 8–16 SATA drives

• True enterprise controller

• Perfect for TrueNAS / Unraid / ZFS

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7. What I would do with your exact system

Given:

• 2 GPUs

• USB card

• Ethernet card

I’d do:

Onboard

• 8 SATA drives

M.2 slot #1

• NVMe cache

M.2 slot #2

• OCuLink → 4-8 SATA

PCIe x4 slot

• LSI HBA (8 drives)

➡ Total ~20 drives possible

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💡 One important NAS tip:
Gaming boards like this lack ECC support with some CPUs and IPMI, but performance is excellent.

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✅ If you want, tell me:

• Your CPU model

• Case size (how many drives physically fit)

• Which NAS OS (TrueNAS, Unraid, Proxmox)

…and I can design an optimal 20-30 drive layout for this motherboard. It’s actually a surprisingly powerful NAS platform.

if I do nr 7 i lose the usb card that i pass through to a VM and the same with the ethernet card

You’re running into the classic limitation of consumer boards used as NAS/virtualization hosts: not enough PCIe slots once GPUs are involved.

Let’s map the ASUS ROG Crosshair VIII Dark Hero slots first so the options are clearer.

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1. Your motherboard PCIe slot reality

Slots available:

1. PCIe x16_1 (CPU) – normally GPU

2. PCIe x16_2 (CPU) – GPU (runs x8/x8 with slot 1)

3. PCIe x16_3 (chipset) – x4 electrical

4. PCIe x1

So if you're using:

• GPU #1

• GPU #2

• USB controller (for VM passthrough)

• Ethernet card

You’ve already filled all usable slots.

That means:

• No slot left for an HBA

• No slot left for Hyper M.2

So expansion must come from M.2 slots or lane sharing.

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2. Best option for your situation: M.2 → SATA/OCuLink

Use the two M.2 slots as your expansion ports.

Option A – M.2 → 6-port SATA controller

Example chips:

• ASM1166

• JMB585

Each M.2 adapter can give:

• 5–6 SATA ports

So:

Slot	Drives
M.2_1 adapter	6 SATA
M.2_2 adapter	6 SATA
Motherboard SATA	8 SATA

➡ Total = ~20 drives

No PCIe slots used.

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3. M.2 → OCuLink (better than SATA controllers)

Instead of SATA controllers, you can convert M.2 to OCuLink.

Then connect to:

• OCuLink → U.2 NVMe

• OCuLink → SATA backplane

• OCuLink → SAS HBA

Advantages:

• lower latency

• higher bandwidth

• enterprise cabling

An M.2 x4 link can comfortably run:

• 4–8 SATA drives

So:

Slot	Drives
M.2 OCuLink	4–8 drives
M.2 OCuLink	4–8 drives
Motherboard SATA	8 drives

➡ 16–24 drives total

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4. Why Hyper M.2 won’t help you much

The ASUS Hyper M.2 x16 Card V2 requires:

• a x16 slot

• PCIe bifurcation

But your two x16 slots are already used by GPUs.

So it would force you to remove either:

• GPU

• Ethernet

• USB controller

Not ideal for your setup.

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5. Another trick: USB controller via motherboard headers

If your USB passthrough card is just for extra USB ports, you might not need the card.

The ASUS ROG Crosshair VIII Dark Hero already has:

• multiple USB controllers

• USB headers

Often you can pass through the onboard USB controller to a VM instead of using a card.

This frees a PCIe slot.

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6. Best layout without losing your cards

PCIe slots

• GPU 1

• GPU 2

• USB passthrough card

• Ethernet card

Storage

• 8 × motherboard SATA

• M.2 → SATA controller (6 drives)

• M.2 → SATA controller (6 drives)

➡ 20 drives

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7. Ultimate trick (if you want crazy expansion)

You can use a PCIe bifurcation riser:

• x16 → 4 × x4 slots

Then one slot can hold:

• USB card

• Ethernet

• SAS HBA

• etc.

But it requires BIOS bifurcation and physical space.

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💡 One more important question that changes everything:

What CPU are you running?

Example:

• AMD Ryzen 9 5950X

• AMD Ryzen 7 5800X

Because Ryzen CPUs only provide 24 PCIe lanes, and how those lanes are used determines the best expansion strategy.

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If you want, I can also show you a very clever NAS trick using one M.2 slot that gives 20+ drives while keeping all your PCIe cards. Most homelab builders with this board don’t realize it’s possible.

i'm using a 3900x cpu. show me the nas trick with one m.2

With the AMD Ryzen 9 3900X and the ASUS ROG Crosshair VIII Dark Hero, you actually have a very powerful trick available: turn one M.2 slot into a full SAS storage controller without using a PCIe slot.

This works because an M.2 NVMe slot is just PCIe x4 lanes. If you convert that slot to a PCIe slot, you can run an HBA exactly like a normal server.

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The “1× M.2 → 16+ drives” NAS trick

Step 1 — Use an M.2 → PCIe x4 adapter

This adapter plugs into the motherboard M.2 slot and gives you a PCIe x4 slot on a cable or riser.

What it does:

M.2 slot (PCIe 4.0 x4)
        ↓
PCIe x4 slot

Now you can install a real SAS HBA.

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Step 2 — Install a SAS HBA

Typical cards:

• LSI 9211-8i SAS HBA

• LSI 9300-8i SAS HBA

These provide:

• 8 SATA/SAS drives directly

But the real magic comes next.

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Step 3 — Add a SAS expander

A SAS expander multiplies ports.

Example:

• Intel RES2SV240 SAS Expander

Connection:

M.2 slot
  ↓
M.2 → PCIe adapter
  ↓
LSI 8-port HBA
  ↓
SAS Expander
  ↓
16–24 SATA drives

Now a single M.2 slot can run 24 drives.

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Why this works well

Bandwidth calculation:

M.2 slot (PCIe 4.0 x4):

• ~8 GB/s

Typical HDD:

• 150–250 MB/s

Even 20 drives only need ~4 GB/s, so the link is still not saturated.

So performance is perfect for NAS workloads.

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Your full system layout

With your current hardware:

PCIe slots

• GPU #1

• GPU #2

• USB passthrough card

• Ethernet card

(no changes required)

Storage

Motherboard:

• 8 SATA drives

M.2 slot #1:

• NVMe cache drive

M.2 slot #2:

• M.2 → PCIe adapter → HBA → SAS expander

Result:

Source	Drives
Motherboard SATA	8
HBA via M.2	16–24
NVMe cache	1

➡ 24–32 total drives possible

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Why homelab NAS builders love this trick

It solves the biggest problem with consumer boards:

• no PCIe slots left

Yet still gives enterprise-style storage expansion.

It’s commonly used in TrueNAS, Unraid, and Proxmox builds.

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One more trick (specific to your board)

The ASUS ROG Crosshair VIII Dark Hero has two M.2 slots.

If you really wanted extreme storage:

• M.2 #1 → HBA (24 drives)

• M.2 #2 → NVMe cache

or

• M.2 #1 → HBA

• M.2 #2 → second HBA

That could theoretically run 40–48 drives from a gaming motherboard.

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✅ If you'd like, I can also show you:

• The exact $15 adapter that works best for M.2 → PCIe

• How to power the SAS expander without a server motherboard

• How some people run 30+ drives on this exact board

Those tricks make a huge difference for NAS builds.

→ HBA → SAS expander. how does a sas expander connect with a HBA

A SAS expander works a bit like a network switch for storage. Instead of each drive connecting directly to the HBA, the expander lets many drives share a few SAS links from the HBA.

Let’s walk through how it connects.

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1. Basic connection layout

Example hardware:

• LSI 9211-8i SAS HBA

• Intel RES2SV240 SAS Expander

Connection looks like this:

CPU / Motherboard
      │
M.2 → PCIe adapter
      │
LSI HBA
      │ (SFF-8087 cable)
      │
SAS Expander
   ├── Drive 1
   ├── Drive 2
   ├── Drive 3
   ├── Drive ...
   └── Drive 24

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2. The actual cables used

Most SAS HBAs use Mini-SAS connectors.

Typical ports on the LSI 9211-8i SAS HBA:

• 2 × SFF-8087 internal SAS ports

Each port carries 4 SAS lanes.

So one cable provides 4 drive channels.

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HBA → Expander cable

You connect them using:

SFF-8087 → SFF-8087 cable

HBA port
   │
SFF-8087 cable
   │
Expander port

This creates an uplink from the HBA to the expander.

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3. Connecting drives to the expander

The expander has many ports.

Example Intel RES2SV240 SAS Expander:

• 24 SAS lanes total

• multiple SFF-8087 ports

Each port can break out to 4 SATA drives using a breakout cable:

SFF-8087 → 4× SATA

Expander port
     │
Breakout cable
 ├── SATA drive
 ├── SATA drive
 ├── SATA drive
 └── SATA drive

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4. Bandwidth explanation

One SAS lane (SAS2):

• 6 Gbps

One SFF-8087 port:

• 4 lanes

• 24 Gbps total

If you connect two HBA ports to the expander:

HBA port 1 ─┐
            ├── Expander
HBA port 2 ─┘

You now have:

• 48 Gbps uplink bandwidth

That easily supports 20+ HDDs.

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5. Powering the SAS expander

The Intel RES2SV240 SAS Expander can be powered two ways:

Option A (server style)

Plug it into a PCIe slot (for power only).

Option B (better for your case)

Use a Molex power connector.

So it can sit anywhere in your case.

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6. Why this setup is popular for NAS

Advantages:

• One controller manages dozens of drives

• Works perfectly with TrueNAS / ZFS

• Very reliable enterprise hardware

• Uses very few PCIe lanes

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7. Example setup for your system

Your system could look like:

M.2 slot
   ↓
M.2 → PCIe adapter
   ↓
LSI 9211-8i
   ↓
Intel SAS expander
   ↓
24 HDDs

Plus:

• 8 motherboard SATA drives

➡ 32 total drives possible

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💡 Important tip:
Flash the LSI 9211-8i SAS HBA to IT mode so it acts as a pure HBA (no RAID). That’s required for TrueNAS, Unraid, and ZFS.

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If you want, I can also show you something even more interesting:

A cheap 36-drive SAS expander setup that uses only one cable from the HBA.

Most homelab NAS builders miss that trick, and it works perfectly with your 3900X system.

What's your question?

My goal is to have 2 dedicate VM's with passthrough for my wife and I.

Basic needs:

1st VM (1 x m.2 (barebone) ; 1 x GPU ; using the rear OI for connectivity)

2de VM (1 x SSD (barebone) ; 1 x GPU ; 1 x USB expansion card ; 1 x ethernet adapter)

running plex, storage server, small web server.

[not completely committed to buy and flash a GPU to have vGPU capabilities ]

storage goals:

2 x nvme for VM passthrough

2 x SSD for VM Passthrough (mirror)

1 x drive passthrough for recovering backup (data recovery if need be)

2 x SSD for cache drives

1 x SSD to spin up VMs

2 x Parity drives

4-6 x storage drives

Going through all the different ideas.

Will the m.2 to oculink to pcie raiser/HBA really work while retaining my PCIe slots and losing 1 x m.2 slot
or should I sacrifice a PCIe x 4 lane for a HBA (and lose the ethernet adapter)
or bifurcate my x16 lane into x8 x4 x4 (not sure what card / adapter to use) ?

And is a 20 drive setup even possible, will the m.2 to PCIe adapter to HBA to SAS expander be worth it?