Intelligence for controlling virtual storage appliance storage allocation

A storage subsystem comprising:

• a storage server having at least one tier of cache;
• a dynamic cache virtual storage appliance (VSA) executing in a virtual machine hosted on hardware resources separate from the storage server, the dynamic cache VSA providing a second tier of the cache, the cache being multi-tiered and hierarchical, each tier including a controller to manage the cache tier;
• and
• a communication protocol for cache communication between a controller the first tier of cache at the storage server and a controller of the second tier of cache at the dynamic cache VSA,
• wherein at least the first tier of cache at the storage server, or the dynamic cache VSA, or both are dynamically resizable, and
• wherein the controllers of the first and second tiers of cache are configured to detect a change of workload characteristics, and to communicate the detected change of workload characteristics to the other controller to cause the other controller to adjust cache size and policy for its cache tier in response to the detected changes.

An article of manufacture comprising a computer-readable storage medium having content stored thereon, which when accessed by a computing device causes the computing device to perform operations including:

• detecting, by a cache device controller for a tier of the multi-tiered cache, a change of workload characteristics at the tier of the multi-tiered cache, where at least one of the tiers of the multi-tiered cache includes a dynamically resizable cache element, and wherein each tier is managed by a controller;
• communicating the detected change of workload characteristics from the controller to a different controller of a different tier of the multi-tiered cache to cause the different controller to adjust its caching size and policy in response to the detected changes, including adjusting a memory allocation size of the dynamically resizable cache element;
• receiving a communication by the controller of the tier of the multi-tiered cache from the controller of the different tier indicating detection by the controller of the different tier of a change of workload characteristics at the different tier when the controller of the different tier detects the change of workload characteristic;
• determining from the communication to alter behavior of the multi-tiered cache in response to the detected change of workload characteristics;
• and
• adjusting how caching is performed in the multi-tiered cache in response to the detected changes at the different tier.