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Abstract

A hybrid solid-state disk (SSD) has multi-level-cell (MLC) or single-level-cell (SLC) flash memory, or both. SLC flash may be emulated by MLC that uses fewer cell states. A NVM controller converts logical block addresses (LBA) to physical block addresses (PBA). Most data is block-mapped and stored in MLC flash, but some critical or high-frequency data is page-mapped to reduce block-relocation copying. A hybrid mapping table has a first-level and a second level. Only the first level is used for block-mapped data, but both levels are used for page-mapped data. The first level contains a block-page bit that indicates if the data is block-mapped or page-mapped. A PBA field in the first-level table maps block-mapped data, while a virtual field points to the second-level table where the PBA and page number is stored for page-mapped data. Page-mapped data is identified by a frequency counter or sector count. SRAM space is reduced.

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First Claim