According to the documentation it should be possible to revert back to OrientDB following a migration to Postgres
However given the Reconcile from blobstore implementation for OrientDB task does not consume blobs created when on the new DB platform, then in actuality, reverting back from PostgreSQL is only feasible if the migrated instance has not created new blobs in the original blobstore - basically if the new migrated instance has not been actually used for anything other than blobstore reads. Since blobs can sometimes get deleted and replaced, the exact semantics of read-only is not well understood for each format and blobstore type.
Make it very clear in documentation that reverting back to using OrientDB is only possible using blobstores and OrientDB databases backed up immediately before upgrading to postgreSQL or H2. ONE CANNOT DO THIS:
1. Migrate from OrientDB to PostgreSQL/H2
2. Use PostgreSQL/H2 for some period of time
3. Stop PostgreSQL/H2 and use OrientDB again against the same blobstores that PostgreSQL/H2 had used, and expect blobs that new DB created to be available.