The first certified SAP Business Warehouse-Enhanced Mixed Workload (BW-EML) standard application benchmark based on a virtual HANA database was recently published by HP. We worked with HP to configure and run this benchmark using a virtual HANA database running on vSphere 5.5 in a monster VM of 64 vCPUs and almost 1TB of RAM. The test was run with a total of 2 billion records and achieved a throughput of 111,850 ad-hoc navigation steps per hour.
The same hardware configuration was used by HP to publish a native only benchmark with the same number of records. In that test, the result was 126,980 ad-hoc navigation steps per hour which is only 12% higher throughput than the virtual HANA result.
Although the hardware setup was the same, this comparison between native and virtual performance has one wrinkle that gave the native system a slight advantage, estimated to be about 5%.
The reason for the estimated 5% advantage for the native system is due to the difference between cores and threads and the maximum number of vCPUs. In the case of the native test, the BW-EML workload was able to exercise all 120 hardware threads of the physical 60 core server. The number of threads is twice the number of physical server cores because these processors utilize Intel Hyper-Threading technology.
In vSphere 5.5 (the current version) the maximum number of vCPUs that can be used in a single VM is 64. Each vCPU is mapped to a hardware thread when scheduled to run. This limits the number of hardware threads that a single VM can use to 64, which means that for this test only slightly more than half of the 120 hardware server threads could be used for the HANA virtual machine. This means that the virtual machine was not able to directly benefit from Hyper-Threading, but was able to use all 60 cores.
The benefit of Hyper-Threading can be as much as 20% to 30% for some applications, but in the case of the BW-EML benchmark, it is estimated to be about 5%. This estimate was found by running the native BW-EML benchmark system with and without Hyper-Threading enabled. Because the virtual machine was not able to use the Hyper-Threads, it is estimated that the native system had a 5% advantage due to its ability to use all 120 threads of the physical server.
In theory, the advantage for the native system could be reduced by either creating a bigger virtual machine or running the native system without Hyper-Threading. If this were done, then the difference between native and virtual should be about 5% smaller and would mean that the difference between native and virtual could shrink to single digits (approximately 7%).
Additional details about the certified SAP BW-EML benchmark configurations used in the tests: SAP HANA 1.0 on HP DL580 Gen8, 4 processors with 60 cores / 120 threads using Intel Xeon E7-4880 v2 running at 2.5 GHz and 1TB of main memory (each processor has 15 cores / 30 threads). The application servers were SAP NetWeaver 7.30 on HP BL680 G7, 4 processors with 40 cores / 80 threads using Intel Xeon E7-4870 running at 2.4 GHz and 1TB of main memory (each processor has 10 cores / 20 threads). The OS used for all servers was SuSE Enterprise Linux Server 11 SP2. The certification number for the native test is 2014009 and the certification number for the virtual test is 2014021.