The two-site VxRail vSAN stretched cluster was built in Dell Technologies labs and validated for SAP HANA by Dell Technologies and VMware. The team installed a WAN emulator physical host to isolate the vSAN traffic between the two sites in the cluster, enabling the introduction of different levels of latency between the sites to measure the performance impact for different distances.
To calculate cable distances between the two sites, the team used 5 ms per kilometer in accordance with the Calculating Optical Fiber Latency reference tool.
The engineering team used a cluster of four P570F VxRail nodes on site A and four P570F VxRail nodes on site B, and then deployed the nodes in a vSAN stretched cluster, as shown in the following figure. Each site hosted six SAP HANA VMs, two per P570F node, with one P570F node used as a standby. The stretched cluster consisted of a total of 12 SAP HANA VMs spanning the two sites.
The teams used the SAP HANA Hardware and Cloud Measurement Tool (HCMT) to perform the tests on the 12 SAP HANA VMs in parallel to ensure that the performance of the SAP HANA and vSAN stretched cluster was compliant with the SAP HANA sub-millisecond log latency KPI and VMware stretched cluster requirements.
The team conducted the HCMT tests first over zero distance as a baseline, and then over various short distances, to measure the performance impact of the SAP HANA KPIs as the latency was introduced. Test results showed that it was possible to achieve distances of up to 30 km between the two sites and still be in compliance with the SAP HANA sub-millisecond log latency KPI.
The team configured four P570F nodes on site A and four P570F nodes on site B with: