-If a block appears in multiple collections with different storage classes, the block will be stored in separate volumes for each storage class, even if that results in overreplication, unless there is a volume which has all the desired storage classes.
+If you change the storage classes for a collection, the data is not moved immediately. The "keep-balance":{{site.baseurl}}/install/install-keep-balance.html service is responsible for deciding which blocks should be placed on which keepstore volumes. As part of the rebalancing behavior, it will determine where a block should go in order to satisfy the desired storage classes, and issue pull requests to copy the block from its original volume to the desired volume. The block will subsequently be moved to trash on the original volume.