Project Capstone was put together a few weeks before VMworld 2015 with the goal of being able to show what is possible with Monster VMs today.  VMware worked with HP and IBM to put together an impressive setup using vSphere 6.0, HP Superdome X and an IBM FlashSystem array that was able to support running four 120 vCPU VMs simultaneously.  Putting these massive Virtual Machines under load we found that performance was excellent with great scalability and a high amount of throughput achieved.

vSphere 6 was launched earlier this year and includes support for virtual machines with up to 128 virtual CPUs which is a big increase from the 64 vCPUs supported in vSphere 5.5. “Monster” virtual machines have a new upper limit and it allows for customers to virtualize even the largest of systems with very hungry CPU needs.

The HP Superdome X used for the testing is an impressive system.  It has 16 Intel Xeon E7-2890v2 2.8 GHz processors.  Each processor has 15 cores and 30 logical threads when Hyper Threading is enabled. In total this is 240 cores / 480 threads.

An IBM FlashSystem array with 20TB of superfast low latency storage was used for the project Capstone configuration.  It provided extremely low latency throughout all testing and provided such great performance that storage was never a concern or issue.  The FlashSystem was extremely easy to setup and use.  Within 24 hours of it arriving in the lab, we were actively running four 120 vCPU VMs with sub millisecond latency.

Large Oracle 12c database virtual machines running on Redhat Enterprise Linux 6.5 were created and configured with 256GB of RAM, pvSCSI virtual disk adapters, and vmxnet3 virtual NICs.  The number of VMs and the number of vCPUs for each VM was varied across the tests.

The workload used for the testing was DVD Store 3 (github.com/dvdstore/ds3).  DVD Store simulates a real online store with customers logging onto the site, browsing products and product reviews, rating products, and ultimately purchasing those products.  The benchmark is measured in Orders Per Minute, with each order representing a complete login, browsing, and purchasing process that includes many individual SQL operations against the database.

This large system with 240 cores / 480 threads, an extremely fast and large storage system, and vSphere 6 showed that even with many monster VMs excellent performance and scalability is possible.  Each configuration was first stressed by increasing the DVD Store workload until maximum throughput was achieved for a single virtual machine.  In all cases this was found to be at near CPU saturation.  The number of VM was then increased so that the entire system was fully committed.   A whitepaper to be published soon will have the full set of test results, but here we show the results for four 120 vCPU VMs and sixteen 30 vCPU VMs.

In both cases the performance of the system when fully loaded with either 4 or 16 virtual machines achieves about 90% of perfect linear scalability when compared to the performance of a single virtual machine.

In order to be able to drive the CPU usage to such high levels all disk IO must be very fast so that the system is not waiting for a response.  The IBM FlashSystem provided .3 ms average disk latency across all tests.  Total disk IO was minimized for these tests to maximize CPU usage and throughput by configuring the database cache size to be equal to the database size.   Total disk IO per second (IOPS) peaked at about 50k and averaged 20k while maintaining the extremely low latency during tests.

These test results show that it is possible to use vSphere 6 to successfully virtualize even the largest systems with excellent performance.

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.

We recently worked with EMC's internal IT organization to study the performance of their largest Oracle RAC instance on vSphere 5.  The results revealed that Oracle RAC, when virtualized with vSphere 5, performed within 7% on average of a corresponding physical environment. The chart below highlights the results from these tests.  

The blue bars are for tests done at a regular level of load and the green bars are for tests done at a 2x level of load.  Results are reported in terms of sum total response time in seconds for the variety of different transactions in the tested workload.

For full details about the tests please refer to the paper – Performance Study of Oracle RAC on VMware vSphere 5.

This paper also provides the performance best practices developed and implemented for Oracle RAC on vSphere 5 for these tests. This information can be used to optimize existing and new installations of Oracle RAC on vSphere.