4.15 Verifying the Disk I/O Scheduler on Linux

For best performance for Oracle ASM, Oracle recommends that you use the Deadline I/O Scheduler.

Disk I/O schedulers reorder, delay, or merge requests for disk I/O to achieve better throughput and lower latency. Linux has multiple disk I/O schedulers available, including Deadline, Noop, Anticipatory, and Completely Fair Queuing (CFQ).
On each cluster node, enter the following command to verify that the Deadline disk I/O scheduler is configured for use:
# cat /sys/block/${ASM_DISK}/queue/scheduler
noop [deadline] cfq

In this example, the default disk I/O scheduler is Deadline and ASM_DISK is the Oracle Automatic Storage Management (Oracle ASM) disk device.

If the default disk I/O scheduler is not Deadline, then set it using a rules file:

  1. Using a text editor, create a UDEV rules file for the Oracle ASM devices:

    # vi /etc/udev/rules.d/60-oracle-schedulers.rules

  2. Add the following line to the rules file and save it:

    ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{queue/rotational}=="0", ATTR{queue/scheduler}="deadline"

  3. On clustered systems, copy the rules file to all other nodes on the cluster. For example:

    $ scp 60-oracle-schedulers.rules root@node2:/etc/udev/rules.d/60-oracle-schedulers.rules

  4. Load the rules file and restart the UDEV service. For example:

    1. Oracle Linux and Red Hat Enterprise Linux

      # udevadm control --reload-rules

    2. SUSE Linux Enterprise Server

      # /etc/init.d boot.udev restart

  5. Verify that the disk I/O scheduler is set as Deadline.