I would like a backup solution that is proportionate to the requirements of a home lab: something that 'makes sense' in terms of backup security (e.g. backups should ultimately reside at a remote location), but where performance/availability etc are not critical considerations.
Both my local and remote locations are residential, and served by reliable, albeit domestic single-line broadband.
Does it make sense to have a backup server locally, and then sync backups to a second backup server at the remote location? Or should I just have a backup server remotely?
You should always have at least one local and one offsite backup:
Whatever backup options you choose, remember to follow the 3-2-1 rule of backups:
3 – Keep 3 copies of any important file: 1 primary and 2 backups.
2 – Keep the files on 2 different media types to protect against different types of hazards.
1 – Store 1 copy offsite (e.g., outside your home or business facility).
https://www.cisa.gov/sites/default/files/publications/data_backup_options.pdf
Depending on your usecase even more might be a good idea:
https://www.unitrends.com/blog/3-2-1-backup-sucks
Please note that such a strategy doesn't need to be a sync to a remote server (be it PBS or something else). I met some guy on a conference who owns a small media business (means he designs leaflets, websites, ads etc for other businesses for a living). His backup strategy is to have two external USB discs. In one week he will save all his data to the first usb drive and unplug it from the PCs. At the end of the week he will bring this device home. The monday after he will take the second device to work for his backups. Although this strategy isn't without it's own problems it's working quite well for his usecase (have at least two backups, one offsite of his office and fitting his budget and (lack of) knowhow (he don't have the money and time to run a server on the internet).
In case of Proxmox VE and Proxmox Backup Server such a strategy woudn't make so much sense since external devices are not directly supported at the moment (although the PBS developers are working on it at the moment, but as far I know now release date is set at the moment).
So it's much easier to go your route (one local PBS, another one on a offsite location).
Pros of local & remote backup servers:
* Backup creation would still occur even if the remote location were unavailable
* Data would be transferred from the local to the remote after de-duplication so less data transfer over the internet
And the local backup/restore itself will take less time due to the higher local transfer speed (a big pro in my book). Another advantage is that you could setup the permissions that the remote server is only allowed to pull from the local server so even in case of a successfull hacker attack your remote backups would still be safe (given that the hacker didn't manage to take over your remote PBS).
The PBS manual has some good pointers on this:
https://pbs.proxmox.com/docs/storage.html#ransomware-protection-recovery
Or is there another conifiguration that makes even more sense?
Depending on your budget and needed size it might be worth to setup PBS on a cheap vserver as offsite backup. This would safe you the trouble with debugging issues with the PBS in your offsite location and the used Internet. Or you could have two offsite PBS (one in the flat of your family member or friend, one of the vserver). In any case I would have a local PBS, even if it's in a VM (which isn't recommended but still better than having no local PBS at all).
