Gremoire

🖥️ How to Add a New Storage Disk to a Proxmox VM (Example: File Server with 300GB Data Disk) ​

When running virtual machines (VMs) on Proxmox, the default VM setup usually has just one disk (the root/system disk). If you’re building a file server or need extra storage, you can easily add another disk (e.g., 300GB) dedicated to data.

This guide will walk you through adding, formatting, and mounting a new storage volume inside a VM.

1. Add a New Disk from Proxmox Web UI ​

  1. Open the Proxmox Web Interface.
  2. Select your VM (e.g., file-server).
  3. Navigate to Hardware → Add → Hard Disk.
  4. Configure:
    • Bus/Device: SCSI (recommended for performance & hotplug support)
    • Storage: Choose your Proxmox storage pool (e.g., local-lvm or data-pool)
    • Disk Size: 300G
  5. Click Add.

Your VM now has a second disk attached, but it is not yet formatted or mounted.

2. Verify Inside the VM ​

Log into your VM and check the disks:

bash
lsblk

Expected output:

sda   64G
└─sda2   64G   /
sdb  300G        <-- New disk (unformatted)

The sdb device is your new 300GB disk.

3. Partition & Format the Disk ​

We’ll create a single partition and format it as ext4.

bash
sudo fdisk /dev/sdb

Inside fdisk:

  • Press n → create a new partition
  • Press w → write changes

Then format the partition:

bash
sudo mkfs.ext4 /dev/sdb1

4. Mount the Disk ​

Create a directory where you’ll mount the new disk (e.g., /data):

bash
sudo mkdir -p /data
sudo mount /dev/sdb1 /data

Verify:

bash
df -h

You should see:

/dev/sdb1   300G   1G  299G   1% /data

5. Make the Mount Permanent ​

By default, mounts are lost after reboot. To make it persistent, add an entry to /etc/fstab.

bash
echo "/dev/sdb1 /data ext4 defaults 0 2" | sudo tee -a /etc/fstab

Reboot to confirm:

bash
sudo reboot

After reboot:

bash
df -h

You should still see /data mounted.

✅ Summary ​

Now your VM has:

  • System disk (/dev/sda, e.g., 64GB, mounted at /)
  • Data disk (/dev/sdb1, 300GB, mounted at /data)

You can use /data as a storage directory for:

  • File uploads
  • Databases
  • Backups
  • Any application needing large storage

⚡ Pro tip: Instead of /dev/sdb1, you can also use the disk’s UUID in /etc/fstab for safer mounting (prevents issues if device names change). Get it with:

bash
blkid /dev/sdb1