Using highly available backend services and redundant web servers allowed us to do patching and upgrades without service interruption. We only needed to have scheduled downtime for ownCloud when doing upgrades to the product itself.

For minor upgrades, it only took a minute or two. For major upgrades, it could take a couple of hours due to database schema changes. Due to the number of users, several thousand, the database was many GB in size. Even with fast disks, it still takes a fair bit of time to write most schema changes to multi-GB tables.

Our backend storage was from EMC Isilon with SMB connections to the webservers. However, any kind of storage environment that can connect to multiple servers will work well. Being just a standard PHP application, like Facebook, it scales very well. You just need to setup the appropriate backend services to scale with it.

In fact, ownCloud will work extremely well in AWS using services like EFS for storage, ElastiCache, Aurora, and Elastic Beanstalk for automatically scaling webservers.

If your needs are more modest, you could just install it on a small NAS running Apache. Even a Raspberry Pi can run ownCloud.