Backups
Creating and restoring backups.

Proxmox backups
Design
From Proxmox, we will be backing up VMs and containers to the TrueNAS that is running in Proxmox.
In Proxmox, we mount the 
alpha/proxmox/snapshots dataset via NFS as 
alpha-snapshots.
Backups from Proxmox are done hourly on the hour (**:00) and copied to 
alpha-snapshots.
In TrueNAS, backups are made from 
alpha/proxmox/snapshots to Backblaze B2.
Configuration
Mount the target volume
Mount the 
alpha/proxmox/snapshots dataset via NFS, call it 
alpha-snapshots.
Make sure to use the dedicated virtual network bridge 
vmbr1. 
Create the backup job
Select Datacenter > Backups, create a backup job like so:
Mind the 
Notification system and 
Mode settings.
The above may change depending on needs, but it's what it's set to at the time of writing.
The only changed setting here is the bandwidth limit. The only reason it's set is to prevent completely hogging the disk I/O for several minutes. Yes, it takes longer as a result, but at least other services using the pool won't be I/O starved.
Configure vzdump
By default, 
vzdump creates temporary files in the target location (where the backup will go). As a result, it will try to symlink unprivileged container filesystems onto the NFS volume. This causes permission problems, even when NFS is set to mapall user/group.
To fix this problem, modify 
/etc/vzdump.conf:
The only line changed is the 
tmpdir: one. Set it to 
/tmp to prevent doing the compression and such on the target volume.