Wuyang Chung
Wuyang Chung is currently working as a freelancer. Previously, Chung worked at Industrial Technology Research Institute as a Windows CE system integrator. After that he worked in ALi as a firmware engineer. His last work was in Hewlett-Packard Taiwan branch as a system software engineer and worked on writing test programs and helping to analyze product issues detected by those test programs.
Session
Logstor uses the idea from log-structured file system to build a virtual disk on top of a physical disk. It is a virtual disk so its size can be larger then the underlying physical disk. It’s log-structured so it treats the underlying disk as a log and transforms the write requests from upper layer file system to log append operations. Since the random write operations are transformed to log append, the random write operations are transformed to sequential write operations.
Logstor is implemented by using FreeBSD’s GEOM framework. This is the second version of this program. The differences with the previous version are:
* The previous version runs in user-level and this version runs in kernel.
* Remove garbage collection and replace it with Stale Sector Recycle (SSR).
* Add new logstor commands snapshot and rollback.
Snapshot command is used to take a snapshot of the virtual disk and the rollback command can revert the virtual disk back to its previous snapshot.