Update Migration: An efficient B+ tree for flash storage

Abstract

More and more evidence indicates that flash storage is a potential substitute for magnetic disk in the foreseeable future. Due to the high-speed random reads, flash storage could improve the performance of DBMS significantly in OLTP applications. However, previous research has shown that small-to-moderate random overwrites on flash are particularly expensive, which implies that the conventional DBMS is not ready to run on the flash storage. In this paper, we propose the design of a variant of B+ tree for flash storage, namely the Update-Migration B+ tree. In the UM-B+ tree, small quantity of updates will be migrated, rather than being executed directly, to its parent node in the form of update records when a dirty node is evicted from main memory. Further accesses to the child node will cause the update records stored in the parent node to be executed when reading the child node from the permanent storage (flash). We propose the detailed structure and operations of UM-B+ tree. We also discuss expanding the UM-B+ tree to the transaction system based on the Aries/IM. Experiments confirm that our proposed UM-B+ tree significantly reduces the random overwrites of B+ tree in a typical OLTP workloads, therefore securing a significant performance improvement on flash storage. © Springer-Verlag Berlin Heidelberg 2010.