Data protection

A non-transitory computer readable medium that stores instructions that once executed by a storage controller of a storage system, cause the storage controller to execute the steps of:

• obtaining retrieval information for retrieving, from a permanent storage space, a subset of cached data units, the subset of the cached data units forms a part of a set of cached data units that are cached in a first cache memory and were destaged to the permanent storage space;
• selecting cached data units that belong to the subset, wherein the selecting is based on an estimate of which cached data units out of the set of cached data units are associated with a majority of access requests aimed to the first cache memory;
• and
• retrieving, using the retrieval information, at least some of the cached data units of the subset from the permanent storage space to a second cache memory, wherein the retrieving occurs in response to an occurrence of a failure to access the first cache memory;
• wherein the second cache memory differs from the first cache memory.