We develop a crash-consistency model for ext4, and use Ferrite to demonstrate unintuitive crash behaviors of the ext4 implementation. We present a formal framework for developing crash-consistency models, and a toolkit, called Ferrite, for validating those models against real file system implementations. Crash-consistency models include both litmus tests, which demonstrate allowed and forbidden behaviors, and axiomatic and operational specifications. This paper presents crash-consistency models, analogous to memory consistency models, which describe the behavior of a file system across crashes.
As a result, it is difficult for application writers to correctly understand the ordering of and dependencies between file system operations, which can lead to corrupt application state and, in the worst case, catastrophic data loss. But the POSIX file system interfaces do not define the possible outcomes of a crash.
Applications depend on persistent storage to recover state after system crashes.
0 kommentar(er)
