docs: private Snapshot createDiskSnapshot(SnapshotDescriptor descriptor) {
      SnapshotFile file = new SnapshotFile(SnapshotFile.createSnapshotFile(
          storage.directory(),
          storage.prefix(),
          descriptor.index()
      ));
      Snapshot snapshot = new FileSnapshot(file, descriptor, this);
      log.debug("Created disk snapshot: {}", snapshot);
      return snapshot;
    }