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iSER: Better Than a Bridge to the Future

By Andrew Walls posted Thu July 23, 2020 08:29 PM


iSER has been called – “a bridge to the future.”

To better understand how this statement may be true, it’s important to note that the future, in terms of information technology, will be given to the fast, the large, the smart, and the cloudy. For those who choose to deploy iSER, and for those of us who recommend it, this is good news.

iSER stands for “iSCSI extensions for RDMA.” It’s a network protocol that extends the Internet Small Computer System Interface (iSCSI) protocol to use Remote Direct Memory Access (RDMA). IBM developed iSCSI in 1998 and presented the standard to the Internet Engineering Task Force in 2000. Because it uses standard Ethernet, iSCSI does not require the expensive and sometimes complex switches and network cards needed to implement many other high-performance network solutions. That makes it less expensive to deploy and easier to manage.[1] This is why Ethernet and iSCSI are the mainstream networking solutions around the world today,1 and why iSER holds so much promise.

RDMA allows computers in a network to exchange data in main memory without involving the processor, cache, or operating system of either computer. RDMA improves throughput and performance because it frees up resources. RDMA also facilitates a faster data transfer rate and lower-latency networking.[2]

Thanks to its RDMA foundation and its ability to reduce SCSI overhead, iSER can achieve ultra-low latencies across standard Ethernet comparable to other Storage Area Network (SAN) protocols such as Fibre Channel (FC). Work on the protocol began in 2002, so iSER is a mature, proven technology. When these two facts are combined with the ubiquity, cost-efficiency, rising throughput rates, and popularity of Ethernet, the future for iSER looks very bright.

But nothing exists in a vacuum; everything has context. What technologies and environments might iSER be deployed with today, and for years into the future? This is an important question for those of us who develop and recommend solutions to enterprise clients. iSER will be simply one part of a much larger puzzle. How will iSER complement the other IT pieces? If we take the last item in the list that began this blog, one thing we can say for certain is that potential iSER customers will have multicloud IT environments – the vast majority of enterprises already do.[3] In order to bring cloud services into their operations, multicloud organizations must use the basic Ethernet/iSCSI backbone. As the cloud becomes more and more prevalent, budget-conscious IT decision-makers will question why they should add the cost and complexity of additional networking hardware and software – when they can get equivalent network performance for less.

And speaking of complexity, research conducted by industry analyst firm Enterprise Strategy Group (ESG) notes that 64% of organizations say IT is more complex compared with two years ago.[4] And the current pandemic doesn’t help: 33% say that more remote workers accessing data center resources puts increased strain on network infrastructure. The future is certainly looking cloudier and more complex, in so many ways; enterprises will find plenty of reasons to choose technologies built to address these challenges.

How else can iSER be legitimately viewed as a bridge to the future? Flash, and now the Non-Volatile Memory Express (NVMe) protocol, are changing the data storage landscape. These technologies drive storage performance up and latency down. Remember that only a few years ago, storage latency in the low milliseconds was a competitive advantage. Now, SAS SSDs offer half-millisecond response times, while NVMe SSDs are down around 125 microseconds, IBM FlashCore Modules offer 70ms latency, and Storage Class Memory (SCM) utilizing NVMe is projected to achieve speeds in the 15ms range. Astonishing.

iSER can accommodate projected storage device latency trends for many years to come. Speaking of acting as a bridge to the future, enterprises are looking ahead to networks utilizing NVMe over Fabrics (NVMeoF), but this protocol isn’t mature or even available yet. Nevertheless, which technology can use the same basic network infrastructure that will eventually host the speeds and efficiency of NVMeoF so that the hassles of transition to it will be minimal? Of course, it’s iSER. And it is available today!

Along with faster and far cloudier, the future will be larger and smarter as well. These two aspects converge in a technology that’s already sweeping across the business and research landscapes like a storm – artificial intelligence (AI). No matter what else may be happening in the IT environments where iSER is deployed, multicloud architectures and AI-driven apps will be a part of it. AI is a voracious data consumer. “Training” AI applications requires lots of data, the more the better. AI use cases such as autonomous driving vehicles will generate as much as a terabyte of data from each vehicle – every day. The networks that enable AI applications will need to support very high volume, high speed data streams. iSER looks perfect for this role.

There are plenty of mainstream use cases right now where iSER can bring many benefits:

  • Anywhere IBM FlashSystem is deployed
  • Fully Ethernet-based data centers, with no Fiber Channel
  • Cloud setups and workloads
  • Enterprises looking for cost-effective solutions for long-distance IP connectivity
  • SAP HANA workloads
  • VMware environments
  • Cluster inter-node communications
  • IBM HyperSwap – organizations where FCIP routers are a cost deterrent for business continuity
  • SAN Volume Controller Stretched Clusters

In fact, iSER brings real advantages for IBM clients right now. While other storage suppliers are waiting for NVMeoF on Ethernet in the future, IBM clients can improve system performance today.

[1] TechTarget definition: iSCSI (

[2] TechTarget definition: RDMA (

[3] IBM Institute for Business Value: Assembling Your Cloud Orchestra, October 2018

[4] Source: ESG Master Survey Results: 2020 Technology Spending Intentions Survey, January 2020.

​​@Tony Sater@Chris Saul @Elisa Ortiz @Maria Altamirano Borrego

1 comment



Thu September 17, 2020 01:41 PM

Hey Andy,
Good post.  The thing that I see, at least in my accounts, blocking adoption of iSER is honestly the iSCSI baggage that it brings with it.  The majority of my accounts (which are, to be fair, large customers who are very invested in Fibre Channel Protocol.  They really seem to have very little interest in even discussing iSER.

Do you see any signs of that changing?