Intra-page cache update in SLC-mode with partial programming in high density SSDs
Résumé
Modern high density SSDs commonly designate a part of their capacity as a cache using an SLC (Single-level Cell)-mode region. Partial programming is then adopted for reducing space fragmentation in the SLC-mode pages, but it exacerbates program disturbance. This paper proposes a partial programming scheme (called intra-page update) by updating hot, small size data inside a given page to minimize the negative impact induced by program disturbance. Moreover, we introduce a novel data movement principle to separate hot and cold write data in the SLC-mode cache when updating the data or carrying out garbage collections. As a result, the hot updated data can be kept in the SLC-mode cache and the cold data will be flushed onto the high density SSD region. Simulation tests on several realistic disk traces show that our proposal improves both bit error rate and I/O performance compared to state-of-the-art methods, without a noticeable decrease in total endurance.
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