The Impact of Flexible Data Placement in a Software Development Environment

Author: Rory Bolt, Senior Fellow, Kioxia Collection: 2025 OCP Global Summit - Expo Hall Sessions

Summary

Kioxia presents experimental results demonstrating that NVMe Flexible Data Placement (FDP), a new SSD technology coming to market in 2025, can dramatically reduce write amplification factor (WAF) in real workloads without any application code changes. FDP allows applications to send hints directing the SSD to group data with similar lifetimes in the same flash blocks, reducing garbage collection overhead. The key innovation demonstrated is that FDP's default placement ID per namespace feature enables separation of short-lived data (temp files, swap space) from long-lived data through simple OS-level file system configuration -- creating separate namespaces with different default placement IDs for /tmp and swap partitions.

The experiment used repeated Linux kernel builds (5 iterations) on a server with 128 GB RAM as a CI/CD workload proxy. Without FDP, the cumulative WAF averaged 2.2x with instantaneous spikes exceeding 600x. With FDP enabled (separate namespace for temp files only), WAF dropped to nearly perfect 1.0x with garbage collection triggering only twice. In a memory-constrained scenario (8 GB RAM, forcing swap activity), WAF without FDP worsened to approximately 3.0x with spikes reaching 6,000x and near-constant garbage collection. With FDP under the same memory pressure, WAF remained near 1.0x. Most remarkably, the memory-constrained FDP scenario showed a 2-3x improvement in actual build runtime because reduced WAF freed internal SSD bandwidth for swap operations, where dependent reads and writes (swap-in requires completed swap-out) were being throttled by garbage collection in the non-FDP case.