Jonathan Hughes

Overview

Jonathan Hughes is an SSD architect at Solidigm who proposed multiple reclaim group FDP for hyperscale storage. He explains that a hypothetical 8 TB SSD with 128 die and one reclaim group per die exposes 8 reclaim unit handles times 128 reclaim groups — 1,024 placement IDs — versus the few handles of single reclaim group FDP, enabling far finer data separation. He describes two host strategies for that array of placement IDs: individual PID, where a host write stream targets one placement ID, and reclaim group stripe, where a stream is striped across a reclaim unit handle over multiple reclaim groups; the two can be combined on one SSD.

Using Solidigm's WAF simulator on a hyperscale workload (cloud database tenants, AI checkpointing, HDD caching) modeled as sequential write streams, he reported write amplification factor (WAF) of 3.06 in standard block mode, 2.6 in single reclaim group mode with three reclaim unit handles, and 1.01 in multiple reclaim group mode with individual PIDs and reclaim group stripes. A Solidigm prototype SSD in development supporting multiple reclaim group FDP measured a real-world WAF of 1.07 on an FIO workload matching the model, showing high correlation to the simulation. He also notes multiple reclaim group FDP lets the host tune per-workload performance — the number of reclaim groups in a stripe sets read/write bandwidth, and isolating workers into individual PIDs or stripes improves quality of service by reducing die and channel contention, independent of WAF-driven QoS gains.