Hybrid flash-based storage constructed with high-density and low-cost flash memory has become increasingly popular in consumer devices in the last decade due to its low cost. However, its poor reliability is one of the major concerns. To protect critical data for guaranteeing user experience, some methods are proposed to improve the reliability of consumer devices with non-hybrid flash storage. However, with the widespread use of hybrid storage, these methods will result in severe problems, including significant performance and endurance degradation. This is caused by the fact that the different characteristics of flash memory in hybrid storage are not considered, e.g., performance, endurance, and access granularity. To address these problems, a critical data backup (CDB) design is proposed to ensure critical data reliability at a low cost. The basic idea is to accumulate two copies of critical data in the fast memory first to make full use of its performance and endurance. Then, one copy will be migrated to the slow memory in the stripe to avoid the write amplification caused by different access granularity between them. By respecting the different characteristics of flash memory in hybrid storage, CDB can achieve encouraging performance and endurance improvement compared with the state-of-the-art. Furthermore, to avoid performance and lifetime degradation caused by the backup data occupying too much space of fast memory, CDB Pro is designed. Two advanced schemes are integrated. One is making use of the pseudo-single-level-cell (pSLC) technique to make a part of slow memory become high-performance. By supplying some high-performance space, data will be fully updated before being evicted to slow memory. More invalid data are generated which reduces eviction costs. Another is to categorize data into three types according to their different life cycles. By putting the same type of data in a block, the eviction efficiency is improved. Therefore, both can improve device performance and lifetime based on CDB. Experiments are conducted to prove the efficiency of CDB and CDB Pro. Experimental results show that compared with the state-of-the-arts, CDB can ensure critical data reliability with lower device performance and lifetime loss whereas CDB Pro can diminish the loss further.

采用高密度和低成本闪存构建的混合闪存存储由于成本低廉，在过去十年中在消费设备中越来越受欢迎。然而，其可靠性差是主要问题之一。为了保护关键数据以保证用户体验，提出了一些方法来提高具有非混合闪存的消费设备的可靠性。然而，随着混合存储的广泛使用，这些方法将导致严重的问题，包括显着的性能和耐久性下降。这是因为没有考虑混合存储中闪存的不同特性，例如性能、耐用性和访问粒度。针对这些问题，提出了关键数据备份（CDB）设计，以低成本保证关键数据的可靠性。其基本思想是首先在快速存储器中积累两份关键数据，以充分利用其性能和耐用性。然后，一份副本将被迁移到条带中的慢速内存，以避免它们之间的访问粒度不同而导致的写入放大。通过尊重混合存储中闪存的不同特性，与最先进的技术相比，CDB 可以实现令人鼓舞的性能和耐用性改进。此外，为了避免备份数据占用过多快速内存空间而导致性能和寿命下降，设计了CDB Pro。集成了两种先进方案。一是利用pSLC（pseudo-single-level-cell）技术使部分慢速内存变得高性能。通过提供一些高性能空间，数据将在被逐出到慢速内存之前得到完全更新。生成更多无效数据，从而降低驱逐成本。 另一种是根据数据的不同生命周期将数据分为三类。通过将相同类型的数据放在一个块中，可以提高逐出效率。因此，两者都可以基于CDB提高器件性能和寿命。通过实验验证了CDB和CDB Pro的效率。实验结果表明，与最先进的技术相比，CDB 可以以较低的设备性能和寿命损失来确保关键数据的可靠性，而 CDB Pro 可以进一步减少损失。