Non-Volatile Solid-State Cache Wear Optimization

The patent divides the flash memory cache into multiple regions with different characteristics (e.g., SLC and MLC regions). Different data types are stored in different regions based on their access patterns and wear characteristics. This local differentiation allows the system to optimize for both performance and wear distribution by placing frequently accessed data in SLC region while using MLC region for less frequently accessed data, thereby resolving the contradiction between cache performance and flash memory reliability.

The patent segments the flash memory into multiple independent regions (SLC and MLC) that can be managed separately. Each region has its own wear leveling and cache management policies. This segmentation allows the system to apply wear leveling at the region level rather than globally, preserving cache content management flexibility within each segment while achieving overall wear distribution. The controller can independently manage data placement and eviction policies in each region without being constrained by global wear leveling restrictions.

The patent implements a nested cache hierarchy where a small, fast SLC region is nested within the larger, slower MLC flash memory. The SLC region acts as a high-speed buffer for frequently accessed data, while the MLC region provides large-capacity persistent storage. This nested structure allows the system to achieve both large cache capacity and fast access latency by strategically placing data in the appropriate nested level, effectively resolving the contradiction between cache capacity/persistence and access speed.