Towards Flash-based Enterprise Databases

摘要

Flash memory is being rapidly deployed as data storage for mobile devices such as PDAs, MP3 players, mobile phones and digital cameras, mainly because of its low electronic power, non-volatile storage, high performance, physical stability, and portability. As its capacity increases and prices drop, flash memory will compete more successfully with lower-end, lower-capacity disk drives. It is thus not inconceivable to consider running a full database system on the flash-only computing platforms or an embedded database system on the lightweight computing devices.One disadvantage of flash memory is that prewritten data cannot be dynamically overwritten. Before overwriting prewritten data, a time-consuming erase operation on the used blocks must precede, which significantly degrades the overall write performance of flash memory. Therefore, it is very important to solve this "erase-before-write" problem. This talk covers three recent results toward flash-based enterprise database applications.First, we will explain how a software module inside flash controller, called 'flash translation layer(FTL)' can deal with the "erase-before-write" problem. In particular, we describe a log block buffer scheme, called FAST(Full Associative Sector Translation) [1].Second, we present a new design called in-page logging (IPL) for flash memory based database systems, which can overcome the limitations of flash memory such as high write latency, and exploits unique characteristics of flash memory to achieve the best attainable performance for flash-based database systems [2].Third, we will show the applicability and potential impact that flash memory SSD (Solid State Drive) has for certain type of storage spaces of a database server where sequential writes and random reads are prevalent. We show empirically that up to more than an order of magnitude improvement can be achieved in transaction processing by replacing magnetic disk with flash memory SSD for transaction log, rollback segments, and temporary table spaces [3].