Reliability and Scalability

Is mergerfs "production ready?"

Yes.

mergerfs has been around for over a decade and used by many users on their systems. Typically running 24/7 with constant load.

At least a few companies are believed to use mergerfs in production environments. A number of NAS focused operating systems includes mergerfs as a solution for pooling filesystems.

Most serious issues (crashes or data corruption) have been due to kernel bugs. All of which are fixed in stable releases.

How well does mergerfs scale?

Users have reported running mergerfs on everything from OpenWRT routers and Raspberry Pi SBCs to multi-socket Xeon enterprise servers.

Users have pooled everything from USB thumb drives to enterprise NVME SSDs to remote filesystems and rclone mounts.

The cost of many calls can be O(n) meaning adding more branches to the pool will increase the cost of certain functions but there are a number of caches and strategies in place to limit overhead where possible.