Thinly provisioned flash cache with shared storage pool

A computer program product for data processing in a computing storage environment by a processor device, the computing storage environment incorporating at least high-speed and lower-speed caches, and managed tiered levels of storage, the computer program product comprising a non-transitory computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions comprising:

• a first executable portion that variably shares a Solid State Device (SSD) tier between the lower-speed cache and the managed tiered levels of storage such that the managed tiered levels of storage are operational on large data segments, and the lower-speed cache is allocated with the large data segments, yet operates with data segments of a smaller size than the large data segments and within the large data segments;
• and
• configures the SSD tier for caching those of the large data segments determined to be uniformly hot, by determining that a heat map is hotter than a predetermined threshold, while refraining from processing data retained in the lower-speed cache until the selected group is fully migrated to the SSD tier;
• wherein if selected data segments are cached in the lower-speed cache and are determined to become uniformly hot, migrates the selected group from the lower-speed cache to the SSD tier.