🚀 NAS – P7 How to Configure Disk Passthrough in Proxmox for Synology DSM

Complete & Safe Configuration Guide

Running Synology DSM on Proxmox (Xpenology or test DSM) requires proper disk passthrough configuration if you want full disk control, stability, and performance.

In this guide, you’ll learn how to configure disk passthrough in Proxmox for Synology DSM safely and correctly.

Disk passthrough is essential if you want DSM to fully control your physical hard drives without performance loss.

Many users make critical mistakes that can lead to:

• ❌ Data corruption

• ❌ Missing disks inside DSM

• ❌ Improper disk detection

• ❌ Boot failure

This tutorial explains the difference between passthrough methods and shows you exactly when and how to use the correct approach.

You will see step-by-step how to:

• 🔍 Identify physical disks

• ⚙️ Configure Proxmox correctly

• 🔗 Attach disks to DSM VM safely

This setup is ideal for:

• 🗄️ NAS deployments

• 💾 Backup servers

• 🏠 Homelab environments

• 🧪 Xpenology testing systems

Follow along carefully to build a reliable NAS solution on Proxmox with confidence.

📌 Understanding Disk Passthrough in Proxmox

When running DSM inside Proxmox, you have two main storage approaches:

1️⃣ Virtual disks (qcow2 or raw on local-lvm)
2️⃣ Physical disk passthrough

For production NAS environments, physical disk passthrough is strongly recommended because:

✅ DSM manages SMART data directly
✅ Better disk health monitoring
✅ Improved performance
✅ Reduced abstraction layer
✅ More stable RAID management

However, incorrect passthrough can destroy existing data — so precision matters.

🖥️ Step 1 – Create the DSM Virtual Machine

First, create your VM in Proxmox.

Disk VM configuration:

Disk VM SATA 5G → storage local-lvm

Write the arc.img file to this SATA disk:

This disk will serve as the boot disk for DSM.

📌 Important:
Disk Boot is sata0

At this stage, the VM is prepared but does not yet contain physical data disks.

🔍 Step 2 – Identify the Physical Disk for Passthrough

Now we identify the real physical disk that DSM will control.

SSH into the host system and list disks:

Example result:

sdb
sdc

The disk to be passed through is named Samsung.

Once you confirm the correct disk name, identify the persistent disk ID:

Example output:

⚠️ Always use disk ID instead of /dev/sdX to prevent issues after reboot.

🧹 If the Disk Has Existing Data (Optional but Recommended)

If the disk contains old partitions and you want to fully format it:

This will wipe partition table metadata.

⚠️ Warning:
This action permanently removes partition information.

Only run this if you are sure the disk does not contain important data.

🔗 Step 3 – Assign the Physical Disk to the VM

Now attach the physical disk to the DSM VM.

Use the following command:

Explanation:

• scsi0 → First data disk

• 106 → VM ID

• Disk Boot remains sata0

At this point:

✔ Boot disk = sata0 (arc.img)
✔ Data disk = scsi0 (physical Samsung disk)

This ensures proper boot order and disk mapping inside DSM.

▶️ Step 4 – Start the VM

Start the DSM virtual machine.

Once booted:

• DSM will detect the passthrough disk

• You can use it as NAS data storage

• Or use it as the NAS OS disk if not yet installed

DSM now has direct control over the physical disk.

🛡️ Best Practices for Stable Disk Passthrough

To avoid common issues:

🔒 Always use /dev/disk/by-id
🔒 Avoid mixing virtual and physical disks in RAID
🔒 Keep Proxmox updated
🔒 Monitor SMART data from DSM
🔒 Do not passthrough disks already mounted in Proxmox

For homelab environments, this configuration provides near-native NAS performance.

For SMB production environments, ensure:

• UPS protection

• Proper cooling

• Backup strategy

• RAID redundancy

🏢 Real-World Use Case

Example deployment:

• Proxmox host with 4 physical drives

• DSM running as VM

• All data disks passed through via scsi

• Boot disk remains virtual

Result:

✔ DSM fully manages RAID
✔ SMART monitoring works correctly
✔ Performance close to bare-metal
✔ Clean virtualization architecture

This setup is commonly used in advanced homelab and cost-optimized SMB infrastructure.

🎯 Final Thoughts

Configuring disk passthrough in Proxmox for Synology DSM is a critical step if you want professional-grade NAS performance inside a virtualized environment.

When done correctly, this method ensures:

• Stability

• Direct hardware control

• Reliable RAID behavior

• Long-term scalability

Whether you’re running Xpenology or testing DSM in Proxmox, mastering disk passthrough is essential for any IT infrastructure engineer.