CXL vs Infiniband: Which One to Choose for High-speed Interconnection?

In the ever-expanding digital landscape, the need for high-speed interconnection technologies has never been more critical. Choosing the right technology can significantly impact the performance and efficiency of computing systems. Two prominent options in the market that have been gaining traction are CXL (Compute Express Link) and Infiniband. In this article, we'll delve into the features and advantages of these technologies to help you make informed decisions for your high-speed interconnection needs.

What Are CXL and Infiniband?

Understanding CXL Technology

Compute Express Link, or CXL, represents a cutting-edge interconnect technology focusing more on general computing systems. CXL leverages a high-speed, low-latency interface to enable seamless communication between CPUs and accelerators, such as GPUs or FPGAs. Key features of CXL include:

• 1. High-speed Data Transfer: CXL boasts impressive data transfer speeds, allowing for efficient communication between compute elements.

• 2. Compatibility: CXL is designed to be compatible with various architectures, making it versatile and adaptable to diverse computing environments.

• 3. Efficient Memory Sharing: CXL supports efficient memory sharing through Cache Coherency functionality.

• 4. Flexible Topology: CXL supports various topologies such as point-to-point, tree, and ring.

Exploring Infiniband Technology

InfiniBand, introduced in 2000 by the InfiniBand Trade Association (IBTA), is renowned for its high-performance, low-latency computer network architecture. It stands out in data centers and high-performance computing clusters due to its outstanding data transmission speed and communication capabilities. Key advantages include:

• 1. High Bandwidth: Infiniband offers substantial bandwidth capabilities, making it suitable for data-intensive applications.

• 2. Low CPU Overhead: By offloading processing tasks from the CPU, Infiniband helps optimize system performance and efficiency.

• 3. Scalability: Infiniband networks are renowned for their scalability, supporting over one hundred thousand nodes. To manage such large-scale networks efficiently, organizations deploy Infiniband switches to ensure seamless communications and optimization.

For more details about Infiniband, please refer to InfiniBand, What Exactly Is It?

How to Choose Between CXL and Infiniband?

When comparing CXL and Infiniband, several key technical specifications need to be considered. Understanding the advantages and disadvantages of each technology is essential for making an informed decision.

• Throughput: InfiniBand boasts a single-link peak throughput of up to 800Gbps, while CXL/PCIe Gen5 interface achieves a peak throughput of 512Gbps.

• Latency: InfiniBand latency can reach as low as about 100ns, and CXL latency is about 500ns. InfiniBand is significantly lower than CXL.

• Scalability: InfiniBand networks can scale to over one hundred thousand nodes, a scale yet to be reached by CXL.

• Business Ecosystem: InfiniBand has a highly mature commercial ecosystem, whereas the ecosystem for CXL is still under development.

• Generalization: CXL focuses on interconnecting general computing systems, whereas InfiniBand leans towards the high-performance computing domain.

• Costs: CXL offers higher cost-efficiency advantages than InfiniBand.

Application Scenarios of CXL and Infiniband

CXL and Infiniband are versatile technologies with diverse application scenarios across various industries.

CXL Applications

CXL is gaining traction in server interconnects, AI training acceleration systems, database acceleration, and storage systems. Its capabilities make it particularly well-suited for workloads requiring high-speed data transfers, memory sharing, and efficient utilization of accelerators.

Infiniband Applications

Infiniband finds extensive use in high-performance computing (HPC) environments, including supercomputers, scientific research facilities, and weather prediction systems. It is also widely employed in data centers for high-speed data storage and processing, cloud computing, and virtualization.

The Technological Developments in CXL and InfiniBand

The unveiling of CXL 1.0 in 2019 represented a significant breakthrough, enabling CPUs to access shared accelerator device memory. Since its successful introduction, the Compute Express Link (CXL) protocols and standards have undergone continuous enhancement and expansion.

• CXL 1.1 focused on enhancing compliance and interoperability while ensuring backward compatibility with the original standard.

• CXL 2.0 incorporated additional features such as switching capabilities for fan-out setups, resource pooling, and support for persistent memory. This version aimed to minimize resource overprovisioning while introducing Link-level Integrity and Data Encryption (CXL IDE) for enhanced security.

• CXL 3.0, released in August 2022, doubled the data rate to 64GT/s and expanded packet size from 68 to 256 bytes. Furthermore, enhancements were made in fabric management, memory sharing, and peer-to-peer communications without introducing extra latency.

InfiniBand continues to evolve with the introduction of groundbreaking technologies aimed at enhancing performance and scalability in high-speed interconnect solutions:

• 56/40G FDR InfiniBand: FDR (Fourteen Data Rate) InfiniBand offers speeds of up to 56 Gbps (56 Gigabits per second) for single data lanes, or 40 Gbps when utilizing QSFP (Quad Small Form-factor Pluggable) connectors.

• 100G EDR InfiniBand: EDR (Enhanced Data Rate) InfiniBand delivers up to 100 Gbps per data lane, catering to the increasing demands of bandwidth-intensive workloads in HPC, cloud computing, and AI (Artificial Intelligence) applications.

• 200Gbps HDR InfiniBand: HDR (High Data Rate) InfiniBand doubles the data rate compared to EDR, reaching up to 200 Gbps per data lane. This higher bandwidth is crucial for handling the growing volumes of data generated by modern computational tasks and facilitating faster interconnectivity between nodes in large-scale systems.

• 400Gbps NDR InfiniBand: NDR (Next Data Rate) InfiniBand pushes up to 400 Gbps per data lane. It represents a significant milestone in interconnect technology, enabling ultra-fast data transfer rates for the most demanding workloads and driving innovation in AI, deep learning, and scientific research.

• 800Gbps XDR InfiniBand: XDR (eXtended Data Rate) InfiniBand marks the forefront of InfiniBand technology, boasting speeds of up to 800 Gbps per data lane. XDR InfiniBand sets new standards for high-performance computing and data center networking, empowering organizations to tackle the most complex computational challenges.

As both CXL and InfiniBand continue to push the boundaries of performance and scalability, we can anticipate further advancements that will revolutionize the way data is transmitted, processed, and utilized in various computing applications.