3.1.7 Checking and Setting the Kernel Parameters

To operate the PRIMECLUSTER-related software, you need to edit the values of the kernel parameters based on the environment.

Perform this setup before restarting the installed PRIMECLUSTER.

Target node:: All the nodes in which PRIMECLUSTER is to be installed

The kernel parameters differ according to the products and components to be used.

Check PRIMECLUSTER Designsheets and edit the value if necessary.

Note

To enable modifications, you need to restart the operating system.

Set an appropriate kernel parameter as follows based on the type of "Characteristics" in each table.

Addition
Set the total number of the recommended values and specified values for system default values and for each software.
Maximum value
Specify the maximum value in the recommended values and specified values for each software.
However, make sure to use the system default value if the maximum value is less than that.

The kernel parameter values differ depending upon:

CF Configuration

Kernel parameter	Characteristics	Value	Remarks (parameter description)
SEMMNI value	Addition	20	Maximum number of semaphore ID in whole system
SEMMNS value	Addition	30	Maximum number of semaphore that can be used in entire system
kernel.shmmax	Maximum value	1048576 + value required for resource database (*1)	Maximum size of shared memory segments
kernel.shmmni	Addition	30	Maximum number of shared memory segments

(*1)

Estimate the value required for resource database according to the following equation:

  Value required for resource database = 2776 x number of resources

Estimate the number of resources according to the following equation:

  Number of resources = Number of disks in shared system devices x (number of shared nodes +1) x 2

  Specify the following in "Number of disks in shared system devices":
   - For a disk array unit, specify the number of logical units (LUN).
   - For other than a disk array unit, specify the number of physical units.
  Specify the number of nodes connected to the shared disk in "number of shared nodes."

Note

For system expansion, if you increase the logical disks, you need to re-estimate the resources and restart each node in the cluster system. If you add disks to the cluster after installation, you must then calculate the resources required for the total number of logical disks after addition.

RMS Configuration

In order to ensure that RMS runs normally, the following kernel parameters need to be set. Therefore, when RMS is installed, the definitions of the parameters in /etc/sysctl.conf are automatically updated if not defined or defined with smaller value than the following "Value".

Kernel parameter	Characteristics	Value	Remarks (parameter description)
kernel.msgmnb	Maximum value	4194304	Byte size of the message queue
kernel.msgmax	Maximum value	16384	Maximum size of the message text
kernel.msgmni	Addition	8192	Maximum number of message queues for the entire system

Note

In PRIMECLUSTER, message queues are used for interprocess communication.
When RMS is running, 2076 message queues are reserved from 0x4d2.
If you are using message queues for any applications, use the range other than above (0x4d2 to 0xcee).
Even if definitions of the kernel parameters in /etc/sysctl.conf are automatically added/updated, change the value as necessary in consideration of the value required by other software and user applications.

Using GFS

Kernel parameter	Characteristics	Value	Remarks (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 semaphore that can be used in the entire system. Add 11 to the current value.

Note

The values used by products and user applications that operate in the PRIMECLUSTER system must also be included in the kernel parameter values.

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

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
```
# sysctl -a | grep shm
kernel.shmmni = 4315
kernel.shmmax = 4000000000

# sysctl -a | grep msg
kernel.msgmnb = 4194304
kernel.msgmni = 8199
kernel.msgmax = 32768
```
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. If the example displayed in step 1 shows the current effective values of the kernel parameters, the edited line becomes the following:
SEMMSL value: 20
SEMMNS value: 131
SEMOPM value: 10
SEMMNI value: 42
kernel.shmmni: 4345
kernel.shmmax: 4000000000
kernel.msgmnb: 4194304
kernel.msgmni: 16391
kernel.msgmax: 32768
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.
  If the example displayed in step 1 shows the current effective values of the kernel parameters, the edited line becomes the following:
  kernel.sem = 20 131 10 42
  kernel.shmmni = 4345
  kernel.shmmax = 4000000000
  kernel.msgmnb = 4194304
  kernel.msgmni = 16391
  kernel.msgmax = 32768
2. Apply the settings.
  To change the kernel parameter values to the values in the settings file, execute the following command:
```
# sysctl -p
```
Check the setting changes in the kernel parameters.
To check whether the kernel parameter values were changed correctly, execute the following commands and display the current values:
```
# sysctl -a | egrep sem
kernel.sem = 20 131 10 42
```
```
# sysctl -a | grep shm
kernel.shmmni = 4345
kernel.shmmax = 4000000000
```
```
# sysctl -a | grep msg
kernel.msgmnb = 4194304
kernel.msgmni = 16391
kernel.msgmax = 32768
```
Check that the displayed values are the values that were determined in step 2.