An Ethernet Storage Fabric, or ESF in short, is the fastest and most efficient way to network storage. It leverages the speed, flexibility, and cost efficiencies of Ethernet with the best switching hardware and software packaged in ideal form factors to provide performance, scalability, intelligence, high availability, and simplified management for scale-out storage and hyperconverged infrastructure. Part 1 of this ESF blog explains what an ESF is, its benefits, and why theESF has gained wide adoption, replacing Fibre Channel in modern datacenters. In Part 2 of this blog, we continue the discussion on how to build an ESF in the right way.
Many traditional datacenter networks are built on a Three-Tier Architecture. In this framework, when a service in one physical domain needs to reach another domain, the traffic often flows north-south. For example, the request from the web server goes upstream to the aggregation and core layers and then travels down to the SAN storage in another physical domain. The response data traverses through three layers in the same fashion but in reverse. The individual switches are often highlatency and built with inherent blocking inside the switch and/or oversubscription on the uplinks, meaning the connections between the switch layers will become bottlenecks if the traffic load increases beyond the original network design.
In scale-out storage or hyperconverged infrastructure (HCI), compute and storage are “glued” into unified resource pools. HCI takes this one step further whereby all applications are virtualized to run on virtual machines (VMs), or containers, and distributed (and migrated) across the compute/storage pools using policy-based automation. Access to the storage pool, data protection mechanisms (replication, backup, snapshots, and/or recovery), and VM or container migration for load balancing and failover now generate a deluge of network traffic between the nodes in the cluster(s), which is called east-west traffic. This large amount of east-west traffic, running through a three-tier network –which is not designed for it—leads to higher rate of oversubscription from the access layer to the aggregation and core layers. This in turn will inevitably cause congestion and high long-tail latencies. The resulting degraded, unpredictable performance is ill-suited for storage I/O’s, especially when using flash storage or when supporting latency sensitive database, analytics, machine learning, or e-commerce workloads.
To overcome these architectural shortcomings, modern datacenters are adopting the Leaf-Spine Architecture for scale-out storage/HCI (and big data analytics, machine learning, private cloud, etc.). The leaf-spine architecture has a simple topology wherein every leaf switch is directly connected to every spine switch and any pair of leaf switches communicates with a single hop, ensuring consistent and predictable latency. By using Open Shortest Path First (OSPF) or Border Gateway Protocol (BGP) with Equal Cost Multi-Pathing (ECMP), your network utilizes all available links, and achieves maximal link capacity utilization. When network traffic increases, adding more links between each leaf and its spine can easily provide additional bandwidth between leaf switches to avoid oversubscription, which helps avoid congestion and latency. Furthermore, as more and more scale-out storage/HCI deployments take the hybrid cloud approach, using Layer-3 protocols with standard-based VXLAN/EVPN will seamlessly scale Layer-2 storage domains across datacenter/cloud boundaries with performance, mobility and security, to ensure business continuity.
ESF has to be a transparent network fabric for scale-out storage and HCI, which means that access to remote data offers almost the same performance as access to local data, from the application’s perspective. This translates into close-to-local predictable latency, line-rate throughput with QoS, and linear scalability to accommodate dynamic, agile data movement between nodes – all in a simple and cost-effective way.
With the leaf-spine architecture, the congestion, increased latency, and unpredictable performance caused by traffic jams in the traditional three-tier network is now gone. Within the datacenter, any storage/HCI I/O transverses the ESF in a single hop if the end points are in the same rack or in three hops if across racks. However, dedicated ESF switches are required to construct the fabric so that storage/HCI traffic, including bursty I/O’s and data flows from faster devices such as NVMe SSDs, can always reach the destination with predictable response time. Using a switch not designed for the demands of an ESF can result in higher and unpredictable network latencies even with the more efficient leaf-spine network designs.As mentioned above, that’s exactly what you are trying to avoid for scale-out storage or HCI.
In addition more and more storage and HCI (and big data, and machine learning) platforms employ RDMA over Converged Ethernet (RoCE) to deliver faster network performance and more efficient CPU utilization. As a result optimized congestion management and QoS are required in the ESF switches, to deliver a non-disruptive and transparent network fabric for business-critical applications.
As the leaf-spine architecture makes ESF extremely easy to scale, the ESF switches need be simple to configure for fast and easy deployment and scale-out. Automated network provisioning, monitoring and management are required for virtualized workloads and storage traffic. So is seamless integration with clouds – secure, isolated and agile workspaces for multiple tenants.
Not every datacenter switch can meet these requirements. Dedicated ESF switches such as Mellanox Spectrum™ switches are required.
Mellanox Spectrum switches are storage optimized. They provide line-rate, zero packet loss, resilient network performance and enable a high-density, scalable rack design, and they are non-blocking both internally and with the number and bandwidth of their uplinks.
In a nutshell, Mellanox Spectrum switches make a perfect foundation for an ESF. Simple to deploy, easy to scale, and free of network bottlenecks, they allow scale-out storage and HCI to truly disaggregate data processing from data location, to achieve performance and scale. And Mellanox Spectrum switches deliver all these benefits in such an efficient way that you can spend less on networking, and more on your data and applications!
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