[ogeiczvm]

I have a nextcloud instance (alongside a few other things). I run it on a $10 VPS (disk is a RAID1 array between the local VPS disk and a remote disk (ceph?) that the provider gives. That's the 1st level of storage redundancy.

I periodically (every 10 minutes) rsync everything across to another VPS (different provider). (you can use mysql replication, mysqldump, etc)

Every hour I run an rsync with --link-dest to a storage VPS and once a month I tar everything up (I take the midnight backup of each day) and it goes to long term storage. The resulting archive is only marginally (10-20%) more than the real size on disk as it mostly contains diffs on top of the actual data. I can failover easily between instances if the primary one goes down so it's reasonably highly available.

If you want less complexity you can use the S3 backend (IIRC nextcloud supports encrypted data at rest) and just ensure that's backed up regularily. Nextcloud itself has versioning for changed data.