PRIMECLUSTER Installation and Administration Guide 4.2 (Linux for Itanium)

A.6.3 Using GFS

When using a GFS shared file system, you must change the kernel parameters shown in the table below.

[Kernel parameters that must be changed]

Kernel parameter	Characteristics	Value	Parameter description
SEMMNI value	Addition	2	Maximum value for semaphore identifiers that can be used in the entire system. Add 2 to the current value.
SEMMNS value	Addition	11	Maximum number of shared memory units that can be used in the entire system. Add 11 to the current value.

During execution, you can use the sysctl(8) utility to change the kernel parameters.

For details about the sysctl operation, see the sysctl(8) manual page.

Described below is the procedure for changing the kernel parameters and setting new values.

1. Check the current values of the kernel parameters.

   To check the current effective values of the kernel parameters, execute the following command:

   # sysctl -a | grep sem

   kernel.sem = 20 90 10 20

   The displayed values represent the following kernel parameters:

   kernel.sem = SEMMSL-value SEMMNS-value SEMOPM-value SEMMNI-value

   If the kernel parameters have not been changed in the /etc/sysctl.conf file, the following default values are displayed:

   kernel.sem = 250 32000 32 128

2. Determine the kernel parameter values.

   The kernel parameter values are determined by the current effective values that were checked in step 1 and the values in the above table. However, if the /etc/sysctl.conf file still contains the default values, indicating that the kernel parameters have not been changed, the values do not need to be changed because they are large enough to handle the parameters used by GFS.

   If the current effective values of the kernel parameters are those shown in step 1, the values to be set are as follows:

    SEMMSL value: 20
    SEMMNS value: 101
    SEMOPM value: 10
    SEMMNI value: 22

3. Change the kernel parameters.

   1. Edit the settings file.

      To set the kernel parameters, use an editor and edit the /etc/sysctl.conf file. Change the values in the following row to the values that were determined in step 2:

      kernel.sem = SEMMSL-value SEMMNS-value SEMOPM-value SEMMNI-value

      If the example displayed in step 1 shows the current effective values of the kernel parameters, the edited line becomes the following:

      kernel.sem = 20 101 10 22

   2. Apply the settings.

      To change the kernel parameter values to the values in the settings file, execute the following command:

      # sysctl -p

4. Check the setting changes in the kernel parameters.

   To check whether the kernel parameter values were changed correctly, execute the following command and display the current values:

   # sysctl -a | egrep sem

   kernel.sem = 20 101 10 22

   Check that the displayed values are the values that were determined in step 2.