chore: docs

Author: ilan-gold

docs/user-guide/performance.md

@@ -113,6 +113,13 @@ bytes within chunks of an array may improve the compression ratio, depending on
 the structure of the data, the compression algorithm used, and which compression
 filters (e.g., byte-shuffle) have been applied.
 
+### Subchunk memory layout
+
+The order of chunks **within each shard** can be changed via the `subchunk_write_order` parameter of the `ShardingCodec` using the `SubchunkWriteOrder` enum or a corresponding string.
+
+By default [`morton`](https://en.wikipedia.org/wiki/Z-order_curve) order provides good spatial locality however [`lexicographic` (i.e., row-major)](https://en.wikipedia.org/wiki/Row-_and_column-major_order), for example, may be better suited to "batched" workflows where some form of sequential reading through a fixed number of outer dimensions is desired. The options are `lexicographic`, `morton`, `unordered` (i.e., random), and `colexicographic`.
+
+
 ### Empty chunks
 
 It is possible to configure how Zarr handles the storage of chunks that are "empty"