Hi, I have two Dell T110 ii. One, with more ram and slightly faster CPU acts as main server. I have it running as NFS server, one VM with a couple of services and two apps (nextcloud and immich). Happy with the setup but worried about hardware of main server failing given age. So I have replication set up (pulls from slave to main). The dataset structure is the same. Is it a matter of installing the same apps and VM on slave, load the config of main onto slave and then just leave it to replication to keep the two machines cloned? I switch on slave only on Sundays to allow replication activity. It is some form of backup I guess, although not perfect.
The answer to this is a little more dependent on what you have running on your primary. If it's solely a file share, then yes. Rsync can be used to simply mirror your pool from one host to another, effectively making a mirror copy.
If you are running applications like jails, plugins, etc, then this answer can sometimes become more complex. Sometimes those applications, jails, whatever only need to have their files copied, which might mean you have to create the application on your backup and then restore the files.
Certain applications that are more complex are affected by a concept called crash consistency. If something uses a database or vm that's reading and writing, when you copy the database it may not be consistent meaning there are things in the middle of being read and written. And that case you needed to have the application stop finish all of its operations and then copy the files. This is likely more complex for may not be applicable to your situation.
If you want to ask specific questions about restoring applications, jails, VMS on trunaz, I would suggest hitting up the trunez community forum after you read the manual a couple of times, they'll eat your lunch if you ask a question that could be simply answered by reading the manual