rsync.net is great for this. They keep ZFS snapshots, so even though you have read/write access you will always have the snapshots stored. So you will be safe

rsync.net is great for this. They keep ZFS snapshots, so even though you have read/write access you will always have the snapshots stored. So you will be safe at least as long as you notice the corruption within the normal 7-day rolling window (there are options for other windows or manual snapshots too IIRC). This should also lead to the question of how up-to-date your backups need to be and is your solution setup for that (is it 1s, 1m, 1h, 1d, etc.)? Define an actual SLA for how much data you can loose and test for that.