The snapshot and restore APIs are very fast and are the preferred way to back up data, but they do have some limitations:
- The backup is a safe Lucene index copy, so it depends on the Elasticsearch version that is used. If you are switching from a version of Elastisearch that is prior to version 5.x, then it's not possible to restore the old indices.
- It's not possible to restore the backups of a newer Elasticsearch version in an older version; the restore is only forward-compatible.
- It's not possible to restore partial data from a backup.
To be able to copy data in this scenario, the solution is to use the reindex API using a remote server.
