A small non-volatile write buffer to reduce storage writes in smartphones

Storage write behavior in mobile devices, e.g., smartphones, is characterized by frequent overwrites of small data. In our work, we first demonstrate a small non-volatile write buffer is effective in coalescing such overwrites to reduce storage writes. We also present how to make the best use of write buffer resource the size of which is limited by the requirement of small form factor. We present two new methods, shadow tag and SQLite-aware buffer management both of which aim at identifying hot storage data to keep in the write buffer. We also investigate the storage behavior of multiple mobile applications and show that their interference can reduce the effectiveness of write buffer. In order to resolve this problem, we propose a new dynamic buffer allocation method. We did experiments with real mobile applications running on a smartphone and a Flash memory-based storage system and obtained average 56.2% and 50.2% reduction in storage writes in single and multiple application runs, respectively.