I have a system of throwing up and tearing down new Lagotto server instances. It restores the MySQL and CouchDB databases from our latest backup each time, but I'm wondering if restoring the CouchDB is necessary. If I have a new Lagotto installation with an old mysql db, am I going to encounter any problems or is it simply inefficient for Sidekiq to be starting with a clean slate?
CouchDB stores data not in MySQL, so you need both. The upcoming 4.0 release (currently in testing, scheduled for release end of April) will drop CouchDB and store everything in MySQL. Redis only stores temporary data, so it is safe to start with a fresh database. The only thing you loose is stats (number of jobs processed, etc.).
Related to this: it is probably a good idea to run MySQL and CouchDB on a separate server, as this makes upgrading Lagotto a bit easier. The only thing stored locally on a Lagotto application server is currently the monthly reports and the logs, and I'm working on getting both of them into distributed systems.