From Crash Consistency to Transactions

Abstract

Modern applications use multiple storage abstractions such as the file system, key-value stores, and embedded databases such as SQLite. Maintaining consistency of data spread across multiple abstractions is complex and error-prone. Applications are forced to copy data unnecessarily and use long sequences of system calls to update state in a consistent manner. Not only does this create implementation complexity, it also introduces potential performance problems from redundant IO and fsync() calls, which fragment disk writes into small, random IOs. In this paper, we propose that the operating system should provide transactions across multiple storage abstractions; we can build such transactions with low development cost by taking advantage of a well-tested piece of software: the file-system journal. We present the design of our cross-abstraction transactions and some preliminary results, showing such transactions can increase performance by 31% in certain cases.