ReFlex
ReFlex: Remote Flash ≈ Local Flash
Summary
ReFlex is a software-based system designed to provide remote access to NVMe Flash storage with performance nearly identical to local Flash access. The system addresses the challenges of significant performance overheads and lack of isolation in existing remote Flash access solutions. ReFlex integrates networking and storage processing in a dataplane kernel to achieve low latency and high throughput with minimal resource requirements. It also includes a Quality of Service (QoS) scheduler to enforce service-level objectives (SLOs) for multiple remote clients.
Metadata
Conference: ASPLOS '17
Authors: Ana Klimovic, Heiner Litz, Christos Kozyrakis
Keywords: Remote Flash Access, NVMe, QoS Scheduler
Key Ideas
Dataplane Kernel Integration: ReFlex uses a dataplane kernel to integrate networking and storage processing, reducing overheads and achieving low latency and high throughput.
QoS Scheduler: Implements a QoS scheduler to enforce tail latency and throughput SLOs for thousands of remote clients, ensuring predictable performance.
High IOPS per Core: Capable of serving up to 850K IOPS per core over TCP/IP networking, adding only 21µs of latency over direct local Flash access.
Major Advantages/Contributions
Performance: Provides remote Flash access with performance comparable to local Flash, significantly reducing latency and resource overheads.
Scalability: Supports thousands of remote clients with predictable performance, thanks to the QoS scheduler.
Open Source: ReFlex is available as open-source software, facilitating further research and development.
Major Weaknesses
Hardware Dependency: Performance heavily relies on the capabilities of the NVMe Flash devices and network infrastructure.
Complexity: The integration of networking and storage processing in the dataplane kernel may introduce complexity in deployment and maintenance.
Methodology
Dataplane Execution Model: Uses a polling-based execution model to process requests without interruptions, improving locality and reducing unpredictability.
QoS Scheduling Algorithm: Employs a token-based scheduling algorithm to manage I/O requests and enforce SLOs for latency and throughput.
Experimental Evaluation: Performance evaluated using various benchmarks, comparing ReFlex with local Flash access and other remote Flash access solutions like iSCSI.
Major Results (and Implications)
Low Latency: ReFlex adds only 21µs of latency over direct local Flash access, achieving 99µs tail latency for 4KB random read requests.
High Throughput: Supports up to 850K IOPS per core, with the ability to saturate 1M IOPS of a high-end NVMe device using two cores.
QoS Enforcement: Effectively enforces latency and throughput SLOs for multiple tenants, ensuring predictable performance even under high load.
Key Terms and Concepts
NVMe: Non-Volatile Memory Express, a protocol for accessing high-speed storage media.
QoS Scheduler: A mechanism to manage and guarantee performance metrics like latency and throughput for multiple clients.
Dataplane Kernel: A kernel design that integrates networking and storage processing to optimize performance.
ReFlex demonstrates the feasibility of providing high-performance remote Flash access with minimal overheads, making it a valuable solution for datacenters looking to optimize storage resource utilization.
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