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Adding a Secondary

After creating the Primary RVG of the RDS, go on to adding a Secondary. Use the vradmin addsec command to add a Secondary RVG to an RDS. This command can also be used to add additional Secondary RVGs. The vradmin addsec command can be issued from any host that is already in the RDS.


  Note   If the RDS contains the Primary only, the command must be issued on the Primary. If you issue the vradmin addsec command on the Secondary to be added to the RDS, the command fails as expected.


The vradmin addsec command performs the following operations by default:


Best practices for adding a Secondary


Prerequisites for adding a Secondary

On the Secondary to be added, do the following:

  Create a disk group with the same name as the Primary disk group.

  Create data volumes of the same names and lengths as the Primary data volumes.

  Create an SRL of the same name as the Primary SRL. Note that the SRL cannot be a volume set or a component volume of a volume set.

  If the Primary RVG includes a volume set, make sure that the component volumes on the Secondary to be added have identical names, lengths, and indices as the component volumes on the Primary.

  Make sure the /etc/vx/vras/.rdg file on the Secondary host to be added to the RDS contains the Primary disk group ID. Ensure that each disk group ID entry in the .rdg file is on a separate line.

The vradmin addsec command checks whether the Primary RVG is authorized to create a corresponding Secondary RVG on the specified Secondary host. A Primary is determined as authorized if the /etc/vx/vras/.rdg file on the specified Secondary host contains the Primary disk group ID. If the Primary contains multiple RVGs in the same disk group, only one entry is required. A plus (+) sign in the /etc/vx/vras/.rdg file on the Secondary host indicates that all Primary RVGs on all hosts are authorized to create a Secondary RVG on the specified Secondary host.

The /etc/vx/vras/.rdg file on the Secondary host is only used for authorization checking when a Secondary is added, or when remote data volumes are synchronized or verified. To perform these operations after a Secondary takes over from the Primary, the original Primary host should also have an /etc/vx/vras/.rdg file containing the disk group ID for the new Primary host.

To display the Primary disk group ID, issue the following command on the Primary host:

# vxprint -l diskgroup

For example, to enable host seattle to create an RVG on Secondary host london the .rdg file on the host london must have the following entries, each on a new line.

1083007373.10.seattle

 To add a Secondary to an RDS

# vradmin -g local_diskgroup addsec local_rvgname pri_hostname \
sec_hostname

The argument local_diskgroup is the name of the disk group on the local host.

The argument local_rvgname is the name of the RVG on the local host.

The arguments pri_hostname and sec_hostname are either resolvable hostnames or IP addresses for the Primary and the Secondary hosts. These names are used as local_host and remote_host attributes while creating RLINKs. The local_host and remote_host specify the network connection to use for the Primary and Secondary RLINKs.

Use the -nodcm option if you do not want to add DCMs to the data volumes. By default, DCMs are automatically added unless the -nodcm option is specified.


  Note   By default, SRL protection on the new Primary and Secondary RLINKs is set to autodcm. If you specify the -nodcm option, the vradmin addsec command disables SRL protection.


Note that the Secondary RVG is added to the disk group with the same name as the Primary disk group, unless specified otherwise using the -sdg option.

Example 1:

This example shows how to add a Secondary host london_priv to the RDS, which contains the RVG hr_rvg. For replication, this example uses a private network with the Primary hostname seattle_priv, Secondary hostname london_priv. On the Secondary, the RVG is added to the same disk group as the Primary, that is, hrdg. This example automatically adds DCMs to the data volumes.

# vradmin -g hrdg addsec hr_rvg seattle_priv london_priv

Example 2:

This example shows how to add the Secondary host london_priv to the RDS, which contains the RVG hr_rvg. It creates the Secondary with the specific Primary and Secondary RLINK names to_london and to_seattle. The RLINK connects the Primary host seattle_priv and the Secondary host london_priv. On the Secondary, the RVG is added to the same disk group as the Primary, that is, hrdg.

# vradmin -g hrdg addsec hr_rvg seattle_priv london_priv \

prlink=to_london srlink=to_seattle