Developers Guide

Performance considerations
46 Dell EMC SC Series with Red Hat Enterprise Linux 7x | CML1071
1. Click the Advanced Options link.
2. Uncheck Restrict Mapping Paths and select the controller to pin the volume to for mapping the
server object.
4.3 Understanding HBA queue depth
Queue depth refers to the number of pending I/O requests. Modifying this value can lead to an improvement
in I/O performance in certain workloads. Generally, increasing queue depth can increase throughput, but
consideration should be taken because increasing this value can also lead to higher I/O latency. Different
applications may benefit from increasing this value, such as environments where the bulk of I/O is small reads
and writes. In environments defined by lower IOPS requirements, but needing higher throughput, this is
achieved by lowering this queue depth setting until optimal levels of performance are achieved.
This value can be changed in the HBA firmware or in the Linux kernel module for the HBA. Keep in mind that
if these two settings have different values, the lower value takes precedence. A good strategy to consider is
setting the HBA firmware to the highest number allowable and then tuning this value downward from within
the Linux kernel module.
Consult section 3 for details on modifying this value for the particular vendor HBA in use.