fix chunk/shard iteration

changes/3299.bugfix.rst

@@ -0,0 +1,6 @@
+Fix a bug in ``create_array`` caused by iterating over chunk-aligned regions instead of
+shard-aligned regions when writing data. To make the distinction between chunks and shards more
+obvious in the ``Array`` API, new properties ``chunk_grid_shape``,
+``shard_grid_shape``, ``nshards``, ``nshards_initialized`` were added to the ``Array`` class.
+Additionally, the behavior of ``nchunks_initialized`` has been adjusted. This function consistently
+reports the number of chunks present in stored objects, even when the array uses the sharding codec.

docs/user-guide/performance.rst

@@ -211,7 +211,7 @@ the time required to write an array with different values.::
    ...         start = time.time()
    ...         arr[:] = value
    ...         elapsed = time.time() - start
-   ...         result.append((elapsed, arr.nchunks_initialized))
+   ...         result.append((elapsed, arr.nshards_initialized))
    ...     return result
    ... # log results
    >>> for write_empty_chunks in (True, False):