I saw Avere was recommended in GCP before, but never find the details, thanks for sharing that. It seems that Avere is close to ObjectiveFS, which also use S3 both for data and metadata.

My guest is that Avere could require a cluster of nodes as the fast layer for write and synchronization. In JuiceFS, Redis is used for synchronization and persisting metadata. Local SSD could used for data read-caching, not for writing.

JuiceFS is in production for 3+ years, we have not find much challenge that was difficult with this design, since it's borrowed from GFS, HDFS and MooseFS, have be proved in production for more than 10 years. I'd like to hear what's the challenge you were facing.