Managing user uploads across a load balanced set up

What are the available strategies for managing file uploads in a load balanced set up?

at present we have the load balancer on www.example.com - then various heads w-s1.example.com, w-s2.example.com …w-sX.example.com

if a user uploads a file it ends up on which ever head that session has connected to.

What’s the ideal way to manage the file so it is accessible from sessions that connect to the other boxes, WITHOUT creating a single point of failure, a minimal delay (a minute or so) is acceptable, longer is not.

as i understand it the DO block storage devices can only be mounted to a single device at a time?

rysnc or similar methods of syncing all boxes might work - but it’s difficult to automate fully so that deletions and mirroring all take place correctly.