Vault 2015

Fsync system call is used for data durability in many applications. However, the latency-sensitive synchronous operations can be delayed under ordered mode in ext4. Since the transaction includes irrelevant data and metadata as well as those of fsynced file, the latency of fsync call can be unexpectedly long. We propose a new journaling scheme which records only the fsync related metadata updates without committing unrelated metadata. By removing or mitigating significantly all adversely affecting factors on fsync latency, the proposed technique can reduce the journal write traffic as well as can reduce the fsync latency.