My host told me that memcache is not supported anymore, so I was trying to switch to Redis.
The Redis server is up and running on port 6379 at localhost, I can connect to it via shell.
But when I activate Redis in config.php, I get the error message:
Fatal error: Redis not installed in /dbtech/dbseo/includes/class_datastore.php on line 551
Is there some additional configuration necessary? Or do I need vB Optimise?