hi setting up HA system is not easy and requires a lot of engineering. If there no absolute need for it I always recommend keeping the system simple and avoid HA setups whenever possible (because such installations are really complex to maintain and troubleshoot often without additional value). very frequent backup often provides more value with still acceptable RTO.
I you still want to go this path you must ensure all 3 important components - webserver, database and storage are HA. I would recommend you look at each of the components separate and try to implement them. you could look at object storage like minio for files, you mentioned DB cluster already and kind of container setup like Docker Swarm or Kubernetes for redundant webserver setup.
We had discussions on this topic in the past - maybe some of them help you