1. A method, comprising: maintaining in a first cache modified and unmodified tracks from a storage system subject to Input/Output (I/O) requests; determining to demote tracks from the first cache; determining whether there are enough tracks ready to demote to form a stride, wherein tracks are written to a second cache in strides defined for a Redundant Array of Independent Disk (RAID) configuration; populating a stride with tracks ready to demote in response to determining that there are enough tracks ready to demote to form the stride; promoting the stride of tracks ready to demote from the first cache to the second cache; demoting from the first cache the stride of tracks promoted to the second cache; and destaging the tracks in the second cache that are modified to the storage system.