Improving SSD lifetime with byte-addressable metadata

Existing solid state drives (SSDs) provide flash-based out-of-band (OOB) data that can only be updated on a page write. Consequently, the metadata stored in their OOB region lack flexibility due to the idiosyncrasies of flash memory, incurring unnecessary flash write operations detrimental to device lifetime. We propose PebbleSSD, an SSD with byte-addressable metadata , or BAM, as a mechanism exploiting the non-volatile, byte-addressable random access memory (NVRAM) inside the SSD. With BAM, PebbleSSD can support a range of useful features to improve its lifetime by reducing redundant flash writes. Specifically, PebbleSSD supports a write-optimized, BAM-based file block mapping to prevent excessive updates of file system index blocks. Furthermore, PebbleSSD allows log-structured file systems to perform fast and efficient log cleaning with minimal flash writes. We have implemented a prototype of PebbleSSD on a commercial SSD development platform, and experimental results demonstrate that PebbleSSD can reduce the amount of data written by log-structured file systems during log cleaning by up to 99%, and PebbleSSD's BAM-based file block mapping can reduce flash writes by up to 33% for a number of workloads.