Developers Guide

Server configuration
37 Dell EMC SC Series with Red Hat Enterprise Linux 7x | CML1071
 For QLogic:
options qla2xxx ql2xmaxqdepth=<value>
 For Emulex:
options lpfc lpfc_hba_queue_depth=<value> lpfc_lun_queue_depth=<value>
The values inside these files can be stacked with other additional key value pairs as needed to define a
complete configuration set.
3.5 SCSI device timeout
The SCSI device timeout of discovered SC Series storage volumes defaults to 30 seconds. Verify the setting
with the following command.
# cat /sys/block/sdX/device/timeout
30
This SCSI device timeout value does not need to be typically changed unless instructed or recommended to
do so by support or application specific directives. If necessary to change this default value, the following
steps are recommended.
To modify the timer that starts the SCSI error handler, run the following command.
# echo X > /sys/block/sdX/device/timeout
X is measured in seconds. Depending on the Linux distribution, this can also be achieved by modifying the
respective udev rule.
To modify the udev rule, edit the /etc/udev/rules.d/60-raw.rules file and append the following lines.
ACTION=="add", SUBSYSTEMS=="scsi", ATTRS{vendor}=="COMPELNT*",
ATTRS{model}=="Compellent Vol*", RUN+="/bin/sh -c 'echo 60
>/sys$DEVPATH/device/timeout'"
To make the above udev rule take effect immediately on the configured devices of the host, run the following
command.
# udevadm trigger –action=add && sleep 2 && multipath –r > /dev/null
The above command triggers an add to occur within udev which calls the previously configured rule to run
against any SC Series volumes found on the host. The shell will then sleep for 2 seconds, allowing the new
udev rule to fully complete before reloading the multipathd service to force any multipath enabled devices to
take on the timeout of their respective child paths. The && portion of the command instructs the shell to only
execute the next commands if the previous command completes successfully.