Tag Archives: WAFL

Here’s what LSFS (WAFL, CASL) is About: Where Log-Structuring Concept Came From, What It’s Good for and Why

Log-Structured File System is a relatively new idea and the technology is obviously effective. However, it is a tool specially crafted for virtualization workload, thus it only works in certain cases. It won’t work out as a common file system for everyday tasks. The idea came from “transaction logs”, which aggregated small random writes into a log to copy them eventually to the “final destination”. Then ZIL (ZFS Intent Log) adopted the same principle in a file system.

LSFS (1)Converged deployment of Storage Spaces Direct for private clouds                                                (Image Credit: Microsoft)

What is good about a Log-Structured File System is that it was literally purpose-built for virtualization. It handles random writes like a marvel, improving performance by order of magnitude on the same hardware configuration. It also helps avoid read-modify-write sequence for parity RAID and offers fast failover recovery.

Most of the problems are associated with sequential reading, garbage collection and free space requirement. However, they all have practical solutions. Log-Structured File System is a good idea all in all, but it should be used with caution, because in terms of tasks and workloads it is not for everyone. Would you like to know more about sky-high performance in virtualization? Check out this article here https://blog.starwindsoftware.com/2015/10/26/heres-what-lsfs-wafl-casl-is-about-where-log-structuring-concept-came-from-what-its-good-for-and-why/ .