OnionDisk: A Log-Structured Write-Optimal Virtual Block Device

The random write performance is critical for a wide range of applications in the cloud. To accelerate such applications, researchers have proposed to realize a log structure in the file system (e.g., F2FS) to support out-of-place updates, so that random data writes can be converted to sequential ones that are more friendly to the physical storage devices. However, file systems are generally complex and internally tightly-coupled, and these proposals usually require writing new file systems from scratch, thus being impractical in many scenarios where the upper-layer applications need specific features and functionalities of existing file systems (like ext4 and xfs).