“Arithmetic is where the answer is right and everything is nice and you can look out of the window and see the blue sky – or the answer is wrong and you have to start over and try again and see how it comes out this time.” ~Carl Sandburg

When we architect SAP on VMware deployments an important topic is how we design for high availability. We have options in the VMware environment from VMware HA, VMware FT and use of in-guest clustering software like Microsoft Cluster Services or Linux-HA. So can we determine a numerical availability for our design expressed as a fraction/percentage  (same metric used to define uptime Service Level Agreements like 99.9% )? Yes, there are ways to estimate this value and one method is explained in the following paper http://www.availabilitydigest.com/public_articles/0712/sap_vmware.pdf . This paper develops an equation to estimate the availability of SAP running on an ESXi cluster expressed as a fraction/percentage. The concepts are taken from other papers at http://www.availabilitydigest.com (a digest of topics on high availability)  and are based on mathematical algebra and probability theory that have been previously used in the IT industry for availability calculations. The availability metric (e.g. 99.9% or 0.999) is essentially a probability hence we use mathematical probability techniques to calculate the overall availability of a system.

The final general equation calculates the availability of an “n” node ESXi cluster sized with “s” number of spares i.e. an “n+s” cluster. It also factors in the software failover times of the single-points-of-failure (SPOF) in the SAP application architecture (database and Central Services). The failover time refers to the time taken for the SPOF to failover and restart on another ESXi host or other virtual machine in the event of an ESXi host failure – this period is important as it corresponds to downtime for the SAP system. The final equation gets a bit heavy on the algebra, but that’s because it models a generic use case. Once you replace the variables with practical “real-world” values, the equation gets easier and that’s when the algebra stops and spread sheeting takes over.

Let’s look at the following example with the following assumptions:

• A five node ESXi cluster running SAP virtual machines, sized with one spare ESXi host i.e. it’s an “n+1” cluster – in the event of one ESXi host failure all impacted virtual machines failover to the remaining four ESXi hosts and all virtual machines continue to run with no loss of performance (the whitepaper covers this example in more detail).
• A loss of two simultaneous ESXi hosts may result in serious performance degradation which we will classify conservatively as downtime for the whole cluster (not really true, but we have to start somewhere, see the whitepaper for caveats).
• The probability of a failover fault is zero i.e. if a VMware HA or in-guest cluster switch over event occurs, the impacted SAP SPOF fails over to remaining ESXi hosts or another virtual machine with no chance of error.
• The availability of a single ESXi host is in the ball park of 0.999 (i.e. “three nines”) – this simplifies the algebra in the general equation (see whitepaper section 4.3.1).

If we apply the above into the general equation from the whitepaper we get the following “simpler equation” specific to this use case.

We can use this equation along with practical values to replace the variables in order to observe how availability is impacted in different scenarios. The variables can be substituted with values obtained from: field experience; data/statistics gathered from actual implementations; reliability specifications from x-86 server vendors; proof-of-concepts / lab work evaluating failover times. The following example scenarios can then be analyzed:

• How does failover time impact the final availability?
• VMware HA adds some extra time for the OS to reboot compared to an active-passive clustering solution, how does this impact availability? VMware HA and clustering solution will have different values for mean time to failover.

At this point we can build a spreadsheet to analyze different scenarios.

It should be noted that this analysis is only considering unplanned downtime due to ESXi host/hardware failure. Other parts of the infrastructure would impact the final availability as experienced by the end-user such as network and storage (see section 3 of the whitepaper). It also does not consider downtime due to software corruptions or bugs or operational mistakes due to human error. Finally, while the formula discussed here is SAP specific the mathematical model can be applied to and adjusted for any ESXi cluster running business applications.

The following best practices for virtualizing SAP can provide useful guidance for virtual CPU, virtual memory, networking and storage setup.

Learn more: Virtualizing Business Critical Applications Whitepaper [39-page PDF]

SAP and VMware are collaborating to provide customers with modern scalable, flexible infrastructure solutions with automated management tools, services, and support to accelerate the Journey to Cloud Computing. For example, vSphere is the only integrated hypervisor in the new release of Landscape Virtualization Management, SAP’s tool for virtualization and infrastructure as a service. Customers with SAP NetWeaver
benefit from an “on-demand” IT environment with a number of benefits:

• The pressure to ensure high availability is intense for SAP managers. VMware virtualization takes advantage of SAP’s high-availability features to enable the software to stay running.
• Upgrades are a fact of life for every SAP landscape and they can be complex and time-consuming and often they take hours or days in a non-virtualized platform. In a virtual environment, new virtual machines can be provisioned in minutes, and then deprovisioned rapidly, recovering the resources.
• As IT budgets continue to shrink, the imperative to lower operating costs gets more urgent—and virtualization can make a real difference. Server consolidation translates directly into lower costs for power, cooling, and space—and boosts the organizations “green” profile in the bargain.
• The IT investment priority in 2012 is virtualization. 71% of surveyed companied plan to invest in SAP virtualization in Germany (Source: DSAG investment survey, 2012.)
• 38% of x86 SAP customers in Germany have 100% virtualized their SAP landscape. (Source: RAAD.)

SAP software also performs well on vSphere. For an apples-to-apples comparison take a look at two-tier benchmark certifications 2011028 (physical) and 2011027 (vSphere5). The virtual result is within six percent of physical, which is completely imperceptible to the SAP Basis admin, but with all the cloning, provisioning, and reliability benefits. Read the details of the SAP benchmark certifications here.

VMware and SAP have been working closely for over five years. In 2007, SAP granted full support to run SAP on VMware. In 2012, SAP went even further and gave support for SAP Sybase ASE. In 2012, VMware engineers are working with SAP to gain support of HANA, SAP’s new in-memory database. Support statements for SAP can be found at the SAP Community Network.

Customer Case in Point
The IT department at Columbia Sportswear Company, the outdoor apparel manufacturer, was looking to get out of the constant churn of physical hardware and into bringing more value to the rest of the business. Exponential growth, combined with the limitations of physical servers, led Columbia to consider virtualizing SAP with VMware and EMC. Through this partnership, Columbia has gained efficiency, reliability, scalability, capacity planning and management, performance tuning and is gaining greater insight into its virtualization layer. The company started by virtualizing IT-based applications, but the new environment proved so beneficial to its business that Columbia decided to move tier-1 workloads, including SAP. Michael Leeper, Senior IT Manager, explained that the decision to virtualize SAP wasn’t a hard one to make. The results Leeper and his team have seen are proof: “S AP running on VMware, running on our architecture, looks and feels exactly like everything else we run.” Because Columbia was running the rest of the company on a very similar virtual architecture, Leeper explained, “We had no significant concerns that putting SAP on that architecture would cause any issues. As a matter of fact, it probably helped us with a lot of things.” At this point, Columbia’s operations are 90 percent virtualized, and IT has been able to deliver business intelligence using new technology, not the technology of the past 10 years.

Learn more: Virtualizing Business Critical Applications Whitepaper [39-page PDF]

By Stacey Meston, Sr. Manager Enterprise Programs

Virtualization continues to define the modern architecture of enterprise IT, establishing both a new model for how applications are run and a path to cloud computing. Still, for some organizations the migration of business-critical applications, such as SAP, to a virtual environment is a foregone conclusion.

SAP Virtualization Lagging Behind

Recently, Aberdeen Group conducted a survey of 100 organizations representing a global audience of enterprises of all sizes. Thirty-five percent (35%) of survey respondents were veteran users of SAP products, who reported that they have deployed SAP for more than 10 years.  Within these enterprises, it was learned that only 31% of SAP deployments have been virtualized.  SAP users appear slower to adopt the concept of virtualization than the general population.  In fact, research of VMware’s own customers indicates the virtualization of SAP is lagging behind other key business-critical applications.

Perceived Challenges to Virtualizing SAP

Aberdeen asked the 69% of survey respondents that have only a physical SAP deployment about the challenges of converting to a virtualized implementation.  Four key areas of concern emerged:

• Uncertainty as to the ROI (40%)
• Fear of harming performance (40%)
• Security (27%)
• Lack of resources to conduct the transition (27%)

Performance issues have been addressed in earlier blog entries.  So let’s focus on the others.

Return on Investment

In a recent TCO Study of SAP running on vSphere conducted by VMS, a specialist in analyzing and optimizing SAP landscapes, a significant savings in TCO was identified and driven by four key items:

• VMware virtualization enables significantly better utilization of hardware, thus reducing power and floor space consumption.
• Faster and smaller hardware also reduces the additional cost for servers, cost for data center and the administration of servers.
• Even more important are savings in the area of upgrade, rollout and improvement projects, for these savings have much more impact on the TCO of SAP systems.
• Flexibility increases in project scenarios like rollout, upgrade and change. Building additional project systems, resetting test systems on the fly, adding training systems, etc. requires no change in adding or buying additional hardware but only in allocation of resources.
•  Decoupling SAP and OS systems from hardware by virtualization enables more focused planning of each: the technical infrastructure and the SAP systems.
• Savings in the area of ongoing cost or operations are smaller, since the majority of the effort there is related to the SAP application itself, which is not affected so much by VMware.

Lack of Resources

Companies planning to virtualize their SAP deployments should consider the use of professional consultants. Over half of the SAP users captured in the Aberdeen survey report that they have virtualized their application with the aid of professional service providers.  Professional consultants have deep experience in virtualizing SAP deployments, which is especially valuable if you feel you do not have the capabilities in your own IT headcount.

Virtualizing your SAP deployment has tremendous upside and the potential for positive returns for your organization.  To fully investigate the potential to your organization, download the full Aberdeen report, “The Case for Virtualizing SAP” or VMS TCO Study, at our VMware Virtualizing SAP Knowledge Vault — a comprehensive resource center for assisting with your SAP virtualization journey.