Proxmox: How To Share Disks With a VM

Michael Bartholomew

Sep. 21, 2022

While setting up a new Virtual Machine (VM) for TrueNAS, I wanted to passthrough existing SATA drives with serial numbers from Proxmox. I am sharing this as I wasn’t able to find simple instructions on how to do this online.

Notes:

These instructions are for QEMU/KVM VMs, and not containers
It assumes you have already created a VM, and know its ID (i.e., 100)
All commands presented below are to be ran inside the Proxmox server’s shell as root, unless otherwise noted

Gather Information

Before we can share the drive with the VM, we must first document the following variables:

VM ID: Proxmox’s Virtual Machine ID (I’m using 100 in this example)
SCSI ID: Proxmox’s SCSI ID for the drive (I’m using scsi2 in this example)
Disk ID: The physical drive’s identifier
Serial Number: The physical drive’s serial number

SCSI ID

To determine which SCSI ID to use:

Open Proxmox’s web interface
View the Hardware screen for the VM you intend to add the disk to
Find the Hard Disk instance with the highest SCSI ID (i.e., scsi1)
Incremement that number by one
Example: If “scsi1” is the SCSI ID for the Hard Disk with the highest instance, then use “scsi2” for the new disk

Disk ID

Finding the drive’s ID requires multiple steps. First, run the following command to determine the disk’s name:

$ lsblk

In my case, the following output was received:

NAME                         MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sdb                            8:16   0   7.3T  0 disk 
sdc                            8:32   0 223.6G  0 disk 
├─sdc1                         8:33   0  1007K  0 part 
├─sdc2                         8:34   0   512M  0 part /boot/efi
└─sdc3                         8:35   0 223.1G  0 part 
  ├─pve-swap                 253:0    0     8G  0 lvm  [SWAP]
  ├─pve-root                 253:1    0  55.8G  0 lvm  /
  ├─pve-data_tmeta           253:2    0   1.4G  0 lvm  
  │ └─pve-data-tpool         253:4    0 140.5G  0 lvm  
  │   ├─pve-data             253:5    0 140.5G  1 lvm  
  └─pve-data_tdata           253:3    0 140.5G  0 lvm  
    └─pve-data-tpool         253:4    0 140.5G  0 lvm  
      ├─pve-data             253:5    0 140.5G  1 lvm

I am interested in passing through the new 7.3TiB drive, so the disk name I am interested in is sdb (highlight added).

Next, run the following command (replacing sbc with the appropriate disk name):

$ ls -l /dev/disk/by-id/ | grep "sdb" | grep -v "wwn-"

The output from the call on my machine reads:

lrwxrwxrwx 1 root root  9 Aug 14 16:26 ata-WDC_WD80EAZZ-00BKLB0_WD-AB1CDEFG -> ../../sdb

This leaves us with:

Disk ID: ata-WDC_WD80EAZZ-00BKLB0_WD-AB1CDEFG

Serial Number

To get the drive’s serial number, run the following command from inside the Proxmox shell, changing sdb in the command below to the name of the drive you are interested in:

$ hdparm -i /dev/sdb

The output from the call on my machine reads:

/dev/sdb:

 Model=WDC WD80EAZZ-00BKLB0, FwRev=80.00A80, SerialNo=WD-AB1CDEFG
 Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq }
 RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=0
 BuffType=unknown, BuffSize=unknown, MaxMultSect=16, MultSect=16
 (maybe): CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=15628053168
 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes:  pio0 pio3 pio4 
 DMA modes:  mdma0 mdma1 mdma2 
 UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6 
 AdvancedPM=no WriteCache=enabled
 Drive conforms to: unknown:  ATA/ATAPI-1,2,3,4,5,6,7

 * signifies the current active mode

The serial number (circled in the output above) appears at the end of the line that begins with Model=. This leaves us with:

Serial Number: WD-AB1CDEFG

Add the Disk

Now it’s time to add the disk to the VM.

Plug your variables into the following command and run it:

$ qm set VM ID -scsiSCSCI ID /dev/disk/by-id/Disk ID,serial=Serial Number

Based on the variable values I collected above, my version of the command looks like:

$ qm set 100 -scsi2 /dev/disk/by-id/ata-WDC_WD80EAZZ-00BKLB0_WD-AB1CDEFG,serial=WD-AB1CDEFG

Validate

To validate that the new disk has been added to the configuration file, run the following command (plugging in your variables):

$ grep scsiSCSI ID /etc/pve/qemu-server/VM ID.conf

My version of the command looks like:

$ grep scsi2 /etc/pve/qemu-server/100.conf

If all went well, you should see something similar to the following:

scsi2: /dev/disk/by-id/ata-WDC_WD80EAZZ-00BKLB0_WD-AB1CDEFG,serial=WD-AB1CDEFG,size=7814026584K

Restart the VM

All that’s left is to restart the VM.