docs - add info. to set blockev at boot.
* docs - add info. to set blockev at boot.
One way to set blockdev at boot.
This will be backported to 6X_STABLE and 5X_STABLE
* docs - update based on review comments.
@@ -314,10 +314,19 @@ vm.dirty_ratio = 10</codeblock></p>
<p>See the manual page (man) for the <codeph>blockdev</codeph> command for more
information about using that command (<codeph>man blockdev</codeph> opens the man
page).</p>
- <note>The <codeph>blockdev --setra</codeph> command is not persistent, it needs to be run
- every time the system reboots. How to run the command will vary based on your system,
- but you must ensure that the read ahead setting is set every time the system
- reboots.</note>
+ <note>The <codeph>blockdev --setra</codeph> command is not persistent. You must ensure
+ the read-ahead value is set whenever the system restarts. How to set the value will
+ vary based on your system.</note>
+ <p>One method to set the <codeph>blockdev</codeph> value at system startup is by adding
+ the <codeph>/sbin/blockdev --setra</codeph> command in the <codeph>rc.local</codeph>
+ file. For example, add this line to the <codeph>rc.local</codeph> file to set the
+ read-ahead value for the disk
+ <codeph>sdb</codeph>.<codeblock>/sbin/blockdev --setra 16384 /dev/sdb</codeblock></p>
+ <p>On systems that use systemd, you must also set the execute permissions on the
+ <codeph>rc.local</codeph> file to enable it to run at startup. For example, on a
+ RHEL/CentOS 7 system, this command sets execute permissions on the
+ file.<codeblock># chmod +x /etc/rc.d/rc.local</codeblock></p>
+ <p>Restart the system to have the setting take effect.</p>
</li>
<li>
<p>Disk I/O scheduler</p>
