THE IMPLEMENTATION OF PREEMPTIVE GARBAGE COLLECTION TO REDUCE GARBAGE COLLECTION-INDUCED TAIL-LATENCY IN SSD RAID

• Main Author: Lutta Putra, Martin
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/43786
• Institution: Institut Teknologi Bandung

Tail-latency is a well-known problem in SSD RAID. It significantly increases I/O latency which in turn makes performance-critical system servers unable to meet common reliability requirements, e.g. I/O latency should be <=100ms at the 98th percentile. One of the main causes of tail-latency in SSD is the Garbage Collection (GC) process. GC renders SSD unable to serve I/O during the process. Recently proposed solutions include ttRAIS which make use of parity reconstruction within RAID to nearly eliminate tail-latency caused by an SSD doing GC. We propose Preemptive Garbage Collection (PGC) to further leverage the effects brought by ttRAIS. By using FEMU, an accurate state-of-the-art flash emulator, we show that PGC by itself is able to reduce tail-latency up to 75%, while PGC and ttRAIS reduce the tail-latency up to 99.9%.