GAZE: Rearchitecting Log-Structured Filesystem for Garbage Collection on Zoned Namespace Flash Storage

We rearchitect the log-structured filesystem for garbage collection on zoned namespace flash storage. We find that the existing garbage collection mechanisms share three design principles that, while reasonable at small scale, become critical limitations when reclaiming gigabyte-scale zones: serial segment cleaning, page-cache-oriented page allocation, and blocking garbage collection. To address these limitations, we develop Pipelined Garbage Collection, Garbage Collection Page Pool, and Selective Blocking. Pipelined Garbage Collection restructures the garbage collection workflow into a four-stage pipeline, enabling concurrent execution of computation- and I/O-intensive stages. Garbage Collection Page Pool preallocates physical pages for garbage collection, avoiding expensive kernel services for allocating and managing pages. Selective Blocking exploits the delayed allocation mechanism of the filesystem, allowing buffered write requests to proceed during garbage collection instead of blocking all types of write() requests. GAZE outperforms F2FS with ZNS support, ZNS+, and P-GC by up to 3× (FIO), ScaleLFS by up to 4.4× (FIO), and IPLFS by up to 1.9× (YCSB-A). GAZE reduces the garbage collection latency to $f13 of that of F2FS.