Proxmox Backup Server Multipath Configuration and Disk Addition

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Proxmox Backup Server Multipath Configuration and Disk Addition

When a disk connected to Proxmox Backup Server (PBS) via SAN comes with dual fiber connections, it may appear as two separate disks. In reality, these are two paths leading to the same physical disk. To avoid confusion and ensure high availability, multipath should be configured so that the system recognizes them as a single device.

This guide explains how to set up multipath on PBS and then add the disk as a datastore.

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1. Install Multipath Tools

apt update
apt install multipath-tools

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2. Configure Multipath

Create or edit the /etc/multipath.conf file and add the following:

defaults {
    user_friendly_names yes
    find_multipaths yes
}

multipaths {
    multipath {
        wwid 36005076812810509b00000000000004e
        alias san_backup40T
    }
}

Note: Replace the wwid value with the one from your own system.
You can find it by running:

multipath -ll

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3. Enable and Restart the Service

systemctl enable multipathd
systemctl restart multipathd

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4. Verify Multipath

multipath -ll
ls -l /dev/mapper/san_backup40T

At this point, the disk should be visible as a single device:
/dev/mapper/san_backup40T

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5. Format the Disk

You can use either ext4 or xfs.

For ext4:

mkfs.ext4 /dev/mapper/san_backup40T

For xfs:

mkfs.xfs /dev/mapper/san_backup40T

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6. Create a Mount Point

mkdir -p /mnt/datastore/backup40t

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7. Edit fstab for Persistent Mount

Add the following line to /etc/fstab:

For ext4:

/dev/mapper/san_backup40T   /mnt/datastore/backup40t   ext4   defaults   0 2

For xfs:

/dev/mapper/san_backup40T   /mnt/datastore/backup40t   xfs   defaults   0 2

Then apply:

mount -a
df -h | grep backup40t

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8. Add Datastore in PBS Web Interface

1. Log in to the PBS web interface.
2. Navigate to Datastore → Add → Datastore.
3. Fill in the fields:
   • Name: backup40t
   • Directory: /mnt/datastore/backup40t
4. Click Add.

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✅ Conclusion

With these steps, you can successfully configure multipath on Proxmox Backup Server and add your SAN disk as a datastore. Multipath ensures redundancy—if one fiber path fails, the other automatically takes over—providing a reliable and highly available backup infrastructure.