Deferred updates for flash-based storage

Abstract

The NAND flash memory based storage has faster read, higher power savings, and lower cooling cost compared to the conventional rotating magnetic disk drive. However, in case of flash memory, read and write operations are not symmetric. Write operations are much slower than read operations. Moreover, frequent update operations reduce the lifetime of the flash memory. Due to the faster read performance, flash-based storage is particularly attractive for the read-intensive database workloads, while it can produce poor performance when used for the update-intensive database workloads. This paper aims to improve write performance and lifetime of flash-based storage for the update-intensive workloads. In particular, we propose a new hierarchical approach named as deferred update methodology. Instead of directly updating the data records, first we buffer the changes due to update operations as logs in two intermediate in-flash layers. Next, we apply multiple update logs in bulk to the data records. Experimental results show that our proposed methodology significantly improves update processing overhead and longevity of the flash-based storages.