On other (non-Laravel) projects, I've used a nfs share that's mounted from all of the different web servers, but that leaves you with one point of failure and a potential bottleneck.
I wasn't sure if there was a better way to handle this.
@CraftThatBlock - have you thought about setting up mirrored servers for failover? For example, I have servers in the SF DigitalOcean farm, but would like to set up mirrors in New York, as either place has issues every once in a while, taking the servers down. I'd be interested in a redundant always-on server setup using Forge. :)
Thanks @CraftThatBlock -- helpful scaling tutorial. Also, even though the above URL recommended by @MajidCS is Russian and video only, I concur it was very useful!