About the LLT and GAB configuration files


About the LLT and GAB configuration files
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Low Latency Transport (LLT) and Group Membership and Atomic Broadcast (GAB) are VCS communication services. LLT requires /etc/llthosts and /etc/llttab files. GAB requires /etc/gabtab file.

Table: LLT configuration files lists the LLT configuration files and the information that these files contain.

Table: LLT configuration files

File	Description
/etc/default/llt	This file stores the start and stop environment variables for LLT: LLT_START - Defines the startup behavior for the LLT module after a system reboot. Valid values include: 1 - Indicates that LLT is enabled to start up. 0 - Indicates that LLT is disabled to start up. LLT_STOP - Defines the shutdown behavior for the LLT module during a system shutdown. Valid values include: 1 - Indicates that LLT is enabled to shut down. 0 - Indicates that LLT is disabled to shut down. The installer sets the value of these variables to 1 at the end of VCS configuration. If you manually configured VCS, make sure you set the values of these environment variables to 1.
/etc/llthosts	The file llthosts is a database that contains one entry per system. This file links the LLT system ID (in the first column) with the LLT host name. This file must be identical on each node in the cluster. A mismatch of the contents of the file can cause indeterminate behavior in the cluster. For example, the file /etc/llthosts contains the entries that resemble: 0 sys1 1 sys2
/etc/llttab	The file llttab contains the information that is derived during installation and used by the utility lltconfig(1M). After installation, this file lists the LLT network links that correspond to the specific system. For example, the file /etc/llttab contains the entries that resemble: set-node sys1 set-cluster 2 link en1 /dev/dlpi/en:1 - ether - - link en2 /dev/dlpi/en:2 - ether - - set-node sys1 set-cluster 2 link en1 /dev/en:1 - ether - - link en2 /dev/en:2 - ether - - The first line identifies the system. The second line identifies the cluster (that is, the cluster ID you entered during installation). The next two lines begin with the link command. These lines identify the two network cards that the LLT protocol uses. If you configured a low priority link under LLT, the file also includes a "link-lowpri" line. Refer to the llttab(4) manual page for details about how the LLT configuration may be modified. The manual page describes the ordering of the directives in the llttab file.

File

Description

/etc/default/llt

This file stores the start and stop environment variables for LLT:

LLT_START - Defines the startup behavior for the LLT module after a system reboot. Valid values include:

1 - Indicates that LLT is enabled to start up.

0 - Indicates that LLT is disabled to start up.
LLT_STOP - Defines the shutdown behavior for the LLT module during a system shutdown. Valid values include:

1 - Indicates that LLT is enabled to shut down.

0 - Indicates that LLT is disabled to shut down.

The installer sets the value of these variables to 1 at the end of VCS configuration.

If you manually configured VCS, make sure you set the values of these environment variables to 1.

/etc/llthosts

The file llthosts is a database that contains one entry per system. This file links the LLT system ID (in the first column) with the LLT host name. This file must be identical on each node in the cluster. A mismatch of the contents of the file can cause indeterminate behavior in the cluster.

For example, the file /etc/llthosts contains the entries that resemble:

    0      sys1
    1      sys2

/etc/llttab

The file llttab contains the information that is derived during installation and used by the utility lltconfig(1M). After installation, this file lists the LLT network links that correspond to the specific system.

For example, the file /etc/llttab contains the entries that resemble:

    set-node sys1
    set-cluster 2
    link en1 /dev/dlpi/en:1 - ether - -
    link en2 /dev/dlpi/en:2 - ether - -

    set-node sys1
    set-cluster 2
    link en1 /dev/en:1 - ether - -
    link en2 /dev/en:2 - ether - -

The first line identifies the system. The second line identifies the cluster (that is, the cluster ID you entered during installation). The next two lines begin with the link command. These lines identify the two network cards that the LLT protocol uses.

If you configured a low priority link under LLT, the file also includes a "link-lowpri" line.

Refer to the llttab(4) manual page for details about how the LLT configuration may be modified. The manual page describes the ordering of the directives in the llttab file.

Table: GAB configuration files lists the GAB configuration files and the information that these files contain.

Table: GAB configuration files

File

Description

/etc/default/gab

This file stores the start and stop environment variables for GAB:

GAB_START - Defines the startup behavior for the GAB module after a system reboot. Valid values include:

1 - Indicates that GAB is enabled to start up.

0 - Indicates that GAB is disabled to start up.
GAB_STOP - Defines the shutdown behavior for the GAB module during a system shutdown. Valid values include:

1 - Indicates that GAB is enabled to shut down.

0 - Indicates that GAB is disabled to shut down.

The installer sets the value of these variables to 1 at the end of VCS configuration.

If you manually configured VCS, make sure you set the values of these environment variables to 1.

/etc/gabtab

After you install VCS, the file /etc/gabtab contains a gabconfig(1) command that configures the GAB driver for use.

The file /etc/gabtab contains a line that resembles:

    /sbin/gabconfig -c -nN

The -c option configures the driver for use. The -nN specifies that the cluster is not formed until at least N nodes are ready to form the cluster. Veritas recommends that you set N to be the total number of nodes in the cluster.

Note:

Veritas does not recommend the use of the -c -x option for /sbin/gabconfig. Using -c -x can lead to a split-brain condition. Use the -c option for /sbin/gabconfig to avoid a split-brain condition.