+For fast storage, it is generally not useful to specify higher
+values than the default due to the top-level producer process
+being a bottleneck.
+
+Default: the number of online CPUs, up to 4 (3 shard workers, 1 producer)
+
+=item --skip-docdata
+
+Do not store document data in Xapian, reducing Xapian storage
+overhead by around 1.5%.
+
+Warning: this option prevents rollbacks to public-inbox 1.5.0
+and earlier.
+
+Available since public-inbox 1.6.0 (PENDING).