VMware recently published a whitepaper that demonstrates VMware vSphere 4’s excellent performance and scalability with SAP ERP software. The paper presents results of several experiments using VMware vSphere and SAP software with both the Microsoft Windows Server 2008 and SUSE Linux 10.2 operating systems.
First, vSphere’s support for nested page tables (AMD Rapid Virtual Indexing, and Intel Extended Page Tables) is shown to provide a 15-82% performance boost for SAP's most MMU-intensive memory models. Next, the paper presents a "scale-up" study, comparing n-way virtual machines to n-way physical machines (see figure); using an SAP application load test, vSphere supported up to 95% of the users achieved on physical machines. The paper also shows that vSphere maintains fairness during CPU overcommitment for an SAP workload and that a performance benefit can be realized when large pages are configured on the host and guest.
The results in the paper suggest that to run SAP in a virtual machine most efficiently, one should adopt the following best practices:
- Run with no more vCPUs than necessary.
- Use the newest processors (e.g., “AMD Opteron 2300/8300 Series” or “Intel Xeon 5500 Series”) to exploit vSphere's support of hardware nested page tables.
- Limit virtual machine size to fit within a NUMA node.
- Configure guest operating system and applications for large pages.
- If using a processor with hardware nested page tables (RVI or EPT) and Linux, choose the Std memory model
- If using a processor with hardware nested page tables (RVI or EPT) and Windows 2008, convenience should dictate the choice of memory model as it has only a minor effect on performance.