Thanks for the insight Scott! Just as a final (for now) update, I went on trying to use a cluster FS on a multiattach EBS (i.e. shared block storage). I tried both GFS2 and OCFS2. I couldn't make it work at all with GFS2. OCFS2 somewhat worked (and was so much simpler to set up), but I still had some cluster issues with it, with servers starting hanging from time to time. I'm giving it up for now, I'll get back at it later. Migrating my SQLite databases to an SQL server on AWS RDS may solve the SQL issue. However I also need to share non SQL(Lite) files between servers. I could use RDS for the SQL part, and EFS for other files. But even for other files it seems performance would be a lot better with a shared block storage than with EFS. If I can succeed at setting up a stable shared block storage + cluster FS at some point, I'll test just putting my SQLite databases for a while there, see how that works out. Thanks again for all the help and suggestions folks, I learned stuff and at least I've got more options now!