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Proxmox Disk Passthrough

Pass physical disks directly to Proxmox VMs

Overview

Disk passthrough allows VMs to access physical disks directly, bypassing the Proxmox storage layer. Useful for:

  • NAS/storage VMs
  • Database servers requiring direct disk access
  • Hardware RAID controllers

Prerequisites

  • Proxmox VE installed
  • Physical disk(s) to passthrough
  • VM already created

Step-by-Step Guide

1. Identify Disk by ID

# List disks with persistent device IDs
lsblk | awk 'NR==1{print $0" DEVICE-ID(S)"}NR>1{dev=$1;printf $0" ";system("find /dev/disk/by-id -lname \"*"dev"\" -printf \" %p\"");print "";}' | grep -v -E 'part|lvm'

Example output: 

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS DEVICE-ID(S)
sda      8:0    0 931.5G  0 disk              /dev/disk/by-id/ata-WDC_WD10EZEX-00WN4A0_WD-WMC4T0123456
sdb      8:16   0   1.8T  0 disk              /dev/disk/by-id/ata-ST2000DM008-2FR102_ZFL12345

Important: Always use /dev/disk/by-id/ paths, not /dev/sdX which can change between reboots.

2. Passthrough to VM

# Syntax
qm set <vm-id> -<interface><number> /dev/disk/by-id/<disk-id>

# Examples
qm set 100 -sata0 /dev/disk/by-id/ata-WDC_WD10EZEX-00WN4A0_WD-WMC4T0123456
qm set 100 -scsi1 /dev/disk/by-id/ata-ST2000DM008-2FR102_ZFL12345
qm set 100 -virtio2 /dev/disk/by-id/nvme-Samsung_SSD_970_EVO_Plus_S4EVNX0N123456

3. Verify Configuration

# Check VM config
qm config 100 | grep -E "sata|scsi|virtio"

Interface Types

Interface Use Case Performance
virtio Linux guests Best
scsi General purpose Good
sata Compatibility Moderate
ide Legacy systems Slowest

Advanced Options

Add with Serial Number

qm set 100 -sata0 /dev/disk/by-id/ata-WDC_WD10EZEX,serial=WD-WMC4T0123456

Multiple Disks (for RAID)

# Pass multiple disks for software RAID in VM
qm set 100 -sata0 /dev/disk/by-id/ata-disk1
qm set 100 -sata1 /dev/disk/by-id/ata-disk2
qm set 100 -sata2 /dev/disk/by-id/ata-disk3

Remove Passthrough

qm set 100 -delete sata0

GUI Method

  1. Select VM → Hardware
  2. Add → Hard Disk
  3. Select Use existing disk
  4. Enter path: /dev/disk/by-id/ata-...

Troubleshooting

Disk Not Visible in VM

# Check disk permissions
ls -la /dev/disk/by-id/ata-*

# Ensure no other process is using the disk
lsof /dev/sdX

Performance Issues

  • Use virtio interface when possible
  • Enable discard for SSDs
  • Check disk queue settings