Rsync backup and prevent file deletion

I have 2 servers, each will have logging data sent to it and I want to rsync that data between each other for offsite backup of the data. So server A will have a set of logs and I want that rsynced to server B and vice versa. But they want to verify that the logs cannot be deleted on the redundant server if the local logs get deleted. So example, they delete todays logs, does an rsync -arv remove files on the target system that are no longer on the source system?

Also, to prevent file deletion on the target server, what is the best way, I was looking at doing chattr -i to the directory structure and that would prevent all but a root user from removing the data.

I'm trying to not have to ingest this into my backup system as it's about 40-60 GB/day of new data per server that is growing per month and has a 1 year retention.