Proxmox Backup Server (PBS) can use “namespaces”. Think of namespaces as a folder on your PBS machine.
If you have multiple PVE machines, they may have duplicate VM IDs. These duplicate IDs will cause problems with backups. By default, backups are stored in the “default” namespace of “blank” under /mnt/datastore/name_of_datastore. Under this we have “vm” and “ct” folders. Under this we have the VM or CT IDs listed. So you can see why duplicate IDs would cause a problem.
The solution is to create and use namespaces.
Create a namespace
On your PBS server on the Datastore option, select the datastore you created. In the upper right corner of the screen is a “Add NS” button. Fill-in this panel and press “Create”. Remember the namespace name you created.
Use the namespace
Note: Once you have created the PBS storage on the PVE server, you cannot change the namespace name.
On your PVE server, click on Datacenter and Storage. Click on “Add” and select “Proxmox Backup Server”. Fill-in this panel and type in the Namespace option with the name of the namespace you previously chose.
How backups are stored in PBS
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# tree -L 2 /mnt/datastore/1TB/
/mnt/datastore/1TB/
├── ct
│ ├── 107
│ ├── 108
│ ├── 109
│ ├── 110
│ ├── 111
│ └── 112
├── lost+found
├── ns
│ └── PVE-Single
└── vm
├── 100
├── 101
├── 102
├── 103
├── 104
├── 105
├── 106
├── 108
├── 113
├── 114
├── 115
├── 116
├── 117
├── 118
├── 119
├── 120
└── 121
Under “ns” you can see the namespace I created.