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iSER, RDMA and IBM’s Spectrum Virtualize family of products

By Archive User posted Tue November 06, 2018 01:03 PM

Data centers are getting wider day by day. In the initial days they were limited to a single physical site. As the adoption grown, data spread across multiple data centers. These data centers are geographically separated by larger distances. Ethernet plays a key role in the next generation data centers where there are multiple use cases handled by the same data center. Ethernet became more and more important day by day with the implementation and integration of private and public cloud with the traditional data centers.

In the current industry implementations, Ethernet connectivity is supported on 1, 10, 25 to 100 Gbps links. This makes it more important for data transfers and data center management through the same network. The traditional ethernet where iSCSI was used for data transfer needed an enhancement using which CPU overheads associated with iSCSI are reduced. These CPU cycles handle large number of IO requests catered by the fat ethernet links. So this reduction in CPU usage can boost the system performance. Using these improvements one can get more with whatever the CPU resources they currently have.

And here comes the RDMA part.

RDMA stands for Remote Direct Memory Access which is implemented long back and much mature and adopted. iSER (iSCSI Extensions over RDMA) is the next generation data center protocol which is gaining a lot of attention. It works with both the most important RDMA protocols backed by different big players of the networking world, RoCE and iWARP.

RoCE is RDMA over Converged Ethernet. It uses UDP as a transport protocol and there are two RoCE versions available, RoCE v1 and RoCE v2. RoCEv2 is a routable internet protocol which we chose to support with IBM’s Spectrum Virtualize family of products from version 8.2.0. iWARP stands for Internet Wide-area RDMA Protocol. This is another RDMA protocol supported by IBM’s Spectrum Virtualize family of products. iWARP works on TCP and both these protocols have their own advantages and limitations. iSER works on both so one can choose the suitable one as per the specific requirements of the data center and overall solution.

In a nutshell, IBM’s Spectrum Virtualize family of products support both the protocols under iSER protocol from version 8.2.0. This gives a large benefit to save the CPU cycles which can be used for other important functions which was a limitation in case of iSCSI.

25Gbps links are used for connecting the IBM’s Spectrum Virtualize family of products as a storage to the servers or hosts with the same 25Gbps adapters installed on it. End to end 25Gbps link gives a complete RDMA path for data transfer. This gives multiple benefits as compared to the other protocols as it saves a lot of CPU cycles which are good for the overall system performance. The 25Gbps links gives a large bandwidth which helps large packets to move faster. Both these features offered by iSER are helping the system performance improvement for IOPs as well as bandwidth.

So if you are planning to expand your data center or planning for a new performance centric use cases, please check the solutions offered by as IBM’s Spectrum Virtualize family of products using iSER.

For more details on the implementation, configuration and benefits, please check