Knowledge

[Andre_Sostizzo]

Virtualization has become so widely accepted that for many companies it is a strategic mandate. The use of dedicated physical servers requires an exception if they are allowed at all. Qlik products have been shown to run very well in virtualized environments. Both Amazon and VMware virtualized environments have been tested with good performance. As with any additional layer between software and hardware, some performance degrade is introduced. Measured values show that average response times are from a few percent to about twenty percent slower in general for virtualized, verified favorable, well-performing hardware. Not adhering to best practices will likely increase any degrade in performance.

Considerations

As with physical servers, it is vital to utilize verified favorable hardware in order to get expected performance. Virtualizing non-favorable servers will not improve performance.

Best Practices

• Always run Qlik products listed as favorable, well-performing hardware.
• If possible, place Qlik products on physical hardware without virtualization.
• If possible, allocate an entire physical server to a single guest OS.
• If many guests are running on the same server, then be wary of resource saturation and whenever possible limit the resources available to non-Qlik Sense or QlikView guests.
• If many guests are running on the same server, dedicate a NUMA node for the Qlik instance.
• Avoid oversubscription of resources (CPU, RAM) at all cost for Qlik Sense and QlikView guests,. Always reserve the required CPU per guest OS.
• Review the Hardware Settings For Best Performance With Qlik Sense 
• Always allocate and reserve all guest memory for guests. 
• Make minimal required settings to Hypervisor (as per above) as they are often very adept at tuning for performance.
• Although Qlik Sense and QlikView are fully supported, it is important but not surprising to note that support of any interactions or issues that arise at the hardware or operating system layer as a result of the use of virtualization is the responsibility of the customer and/or the hypervisor vendor.

Avoid

• Use poorly performing hardware (i.e. hardware that has not been vetted by Qlik)
• Allowing floating allocations of memory to avoid ballooning

Keywords:

• Virtualization: Software added to a physical server in order to allow its resources to be shared between multiple guest OS’s.
• Hypervisor: Software that acts as a virtualization agent. 
• Physical server: A server running a single OS without any virtualization software.
• Underutilization: Low average utilization of available server resources.
• Oversubscription: Through oversubscription, administrators allocate more than their operational target, allowing for even more infrastructure compression in exchange for increased operational risk.
• Memory ballooning: Memory ballooning is a virtual memory management technique used to free unused memory.
• Guest OS: Operating system deployed on a virtualized server.