NAND flash memory has been widely used as data storage devices in consumer electronics, such as tablet computers and smart phones. Logical-to-physical address translation is important for improving the performance of NAND flash-based SSDs. Even though keeping the mapping table in a DRAM can boost the address translation, it is already infeasible to do this as the capacity of SSDs keeps increasing and only a limited part of DRAM will be used as the mapping cache. Orthogonal to the demand-based page-level FTLs, we develop a novel group-level mapping which divides the whole SSD into multiple equal-size groups. To map a logical-page-number to a physical-page-number, it will be translated into a group number and an offset. The group number can be obtained via calculation, and the offset will be retrieved from a recorded mapping entry which can correspond to any position within a group. Group-level mapping reduces the size of mapping table while obtaining the similar flexibility as the page-level mapping. We also design an effective group-level FTL (GFTL) with a block pool management approach. Our simulations show that GFTL improves the hit ratio of mapping cache and thus reduces the average response time.

中文翻译：

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GFTL：闪存转换层中的组级映射，为基于 NAND 闪存的 SSD 提供高效的地址转换

NAND 闪存已广泛用作消费电子产品中的数据存储设备，例如平板电脑和智能手机。逻辑到物理地址转换对于提高基于 NAND 闪存的 SSD 的性能非常重要。尽管将映射表保存在 DRAM 中可以促进地址转换，但由于 SSD 的容量不断增加，并且只有有限的 DRAM 部分将用作映射缓存，因此这样做已经不可行。与基于需求的页面级 FTL 正交，我们开发了一种新颖的组级映射，将整个 SSD 划分为多个相等大小的组。要将逻辑页号映射到物理页号，它将被转换为组号和偏移量。组号可以通过计算得到，并且偏移量将从记录的映射条目中检索，该条目可以对应于组内的任何位置。组级映射减少了映射表的大小，同时获得了与页级映射类似的灵活性。我们还设计了一种具有块池管理方法的有效组级 FTL (GFTL)。我们的模拟表明，GFTL 提高了映射缓存的命中率，从而减少了平均响应时间。