Developers Guide

Performance considerations
44 Dell EMC SC Series with Red Hat Enterprise Linux 7x | CML1071
4 Performance considerations
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 that Linux and storage
administrators can use to fine tune a Linux installation and 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. To analyze your environment, the Dell Performance Analysis Collection Kit (DPACK) is a free
toolkit that is obtained by sending an email to: [e-mail].
Some general guidelines to keep in mind for performance tuning with Linux are:
 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), specific values cannot 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 subsequent changes.
 As a best practice, 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 (when 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.
 An understanding of the differences between block- and file-level data should be established in order
to effectively target the tunable settings for the most effective 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 Dell Storage Manager 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.