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Performance tuning
40 Dell EMC SC Series: Red Hat Enterprise Linux Best Practices | CML1031
4 Performance tuning
This section provides general information and guidance pertaining to some of the more common performance
tuning options and variables available to Linux. This information is not intended to be all-encompassing and
the values used should not be considered final. This section provides a starting point for Linux and storage
administrators to use when fine-tuning their Linux installation to achieve optimal performance.
Prior to making any changes to the following parameters, establish a good understanding of the current
environment and I/O workload. There are numerous methods to accomplish this, including evaluating the
perception of the system or storage administrators based on day-to-day experience with supporting the
environment. Dell EMC Live Optics™ is a free software that collects and analyzes the various aspects of the
environment. For more information, visit https://www.liveoptics.com/.
Dell EMC CloudIQ is a free, software as a service (SaaS) offering that provides continuous monitoring
performance, capacity, configuration, and data protection, and enables administrators to manage storage
proactively by receiving advanced notification for potential issues. Find additional information in the CloudIQ
overview on https://www.dellemc.com/en-us/storage/cloudiq.htm.
Some general guidelines to consider for performance tuning with Linux are as follows:
• Performance tuning is as much an art as it is a science. Since there are a number of variables that
impact performance (I/O in particular), there are no specific values that can be recommended for
every environment. Begin with a few variables and add more variables or layers as the system is
tuned. For example, start with single path, tune, and then add multipath.
• Make one change at a time and then test, measure, and assess the impact on performance with a
performance monitoring tool before making any subsequent changes.
• Make sure the original settings are recorded so the changes can be reverted to a known state if
needed.
• Apply system tuning principles (such as failover) in a non-production environment first (where able)
and validate the changes with as many environmental conditions as possible before propagating
these changes into production environments.
• If performance needs are being met with the current configuration settings, it is generally a best
practice to leave the settings alone to avoid introducing changes that may make the system less
stable.
• Establish an understanding of the differences between block- and file-level data in order to target the
tunable settings that will have the most impact on performance. Although the SC Series array is a
block-based storage device, the support for the iSCSI transport mechanism introduces performance
considerations that are typically associated with network- and file-level tuning.
• When validating whether a change is having an impact on performance, leverage the charting feature
of DSM to track the performance. In addition, be sure to make singular changes between iterations in
order to better track what variables have the most impact (positive or negative) on I/O performance.
4.1 Tuning profiles
RHEL 7.x introduced a new set of tools to assist administrators and storage professionals with tuning RHEL
hosts. This is achieved using two new commands, tuned and tuned-adm, which manage a set of predefined,
performance-tuned profiles.