Setting persistent SCSI timeout

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9

Issue

  • What is the preferred way to permanently tune the default timeout /sys/block/device-name/device/timeout?
  • The RHEL 5 manual describes the way to set SCSI disk timeouts in a persistent way.
  • How to configure the timeout in RHEL6,7,8 & 9?

Resolution

  • A file /etc/udev/rules.d/99-udev.rules containing the following rules will set the timeout permanently:

    ACTION=="add|change", SUBSYSTEM=="scsi" , ATTR{type}=="0|7|14", \
RUN+="/bin/sh -c 'echo 60 > /sys$$DEVPATH/timeout'"

    Another rule without invoking a sub-shell would also work:

    ACTION=="add|change", SUBSYSTEMS=="scsi", ATTRS{type}=="0|7|14", ATTR{device/timeout}="60"

  • RHEL6 would support the same configuration as RHEL5, using the SYSFS keyword in the udev rule. RHEL7,8 & 9 requires the ATTR keyword which is also supported by RHEL6. The rules mentioned in this solution will work on RHEL6,7,8 & 9.

Diagnostic Steps

  • After adding or changing the rules, udev needs to be informed about changed rules:

    # udevadm control --reload

  • With the new rules activated, udev needs to re-enumerate the device

    # udevadm [--debug] test /block/<device>

    or

    # udevadm trigger /dev/<device>

  • cat /sys/block/sd*/device/timeout will also show the configured values:

    60

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