doc: update rgw configuration doc on bucket index sharding feature

Signed-off-by: Yuan Zhou <yuan.zhou@intel.com>

diff --git a/doc/radosgw/config-ref.rst b/doc/radosgw/config-ref.rst
index 0352969e89f094e30ff59644c92ec5b4f5a640d0..b23f2b9d34f2fd62af897be90d48565e129c6c6d 100644 (file)
--- a/doc/radosgw/config-ref.rst
+++ b/doc/radosgw/config-ref.rst
@@ -270,6 +270,17 @@ Ceph configuration file, the default value will be set automatically.
 :Default: ``1000``
 
 
+``rgw override bucket index max shards``
+
+:Description: Represents the number of shards for the bucket index object,
+              a value of zero indicates there is no sharding. It is not
+              recommended to set a value too large (e.g. thousand) as it
+              increases the cost for bucket listing.
+
+:Type: Integer
+:Default: ``0``
+
+
 ``rgw num zone opstate shards``
 
 :Description: The maximum number of shards for keeping inter-region copy