Administering Replication

Changing the Replication Settings

You can change the VVR replication attributes according to your requirements with the vradmin set command. The vradmin set command enables you to set the following VVR replication attributes:

• Replication Mode
• Latency protection
• SRL protection
• Network transport protocol
• Packet size
• Bandwidth limit

For more information on replication settings, see Changing the Replication Settings for a Secondary.

Pausing and Resuming Replication to a Secondary

Pausing an RLINK prevents new and already-queued updates from reaching the Secondary from the Primary, and the Primary and Secondary do not communicate.

The vradmin pauserep command does not provide a way to pause a Secondary RLINK. To do this, use the vxrlink command on the Secondary host. The vradmin resumerep command resumes both types of pauses on the selected RLINKs.

  To pause and resume replication to a Secondary

To pause replication to a specific Secondary in an RDS, specify the Secondary hostname. For an RDS with a single Secondary, you do not have to specify the Secondary hostname.

On any host in the RDS:

1. Pause replication.
     # vradmin -g diskgroup pauserep local_rvgname [sec_hostname]

   where local_rvgname is the name of the RVG on the host where the command is issued, and sec_hostname is the name of the host to which replication is being paused.

2. On the Primary, issue the vxprint command to check that the state of the RLINK is PAUSE.
     # vxprint rlink_name
3. Resume replication to the Secondary.
     # vradmin -g diskgroup resumerep local_rvgname [sec_hostname]

   where local_rvgname is the name of the RVG on the host where the command is issued, and sec_hostname is the name of the host to which replication is being resumed.

Stopping Replication to a Secondary

The vradmin stoprep command can be used to stop replication to a Secondary in an RDS. The vradmin stoprep command can be entered from any host in the RDS.

The vradmin stoprep command fails if the Primary and Secondary RLINKs are not up-to-date. Use the -f option to stop replication to a Secondary even when the RLINKs are not up-to-date.

Before stopping replication, the vradmin stoprep command displays a warning and prompts the user to confirm whether or not to stop replication. To skip this confirmation, use the -s option with the vradmin stoprep command. The -s option to the vradmin stoprep command proves useful in scripts.

To stop replication to a specific Secondary in an RDS, specify the Secondary host name. For an RDS with a single Secondary, you do not have to specify the Secondary host name.

  To stop replication to a specific Secondary in an RDS

The argument local_rvgname is the name of the RVG on the local host and represents its RDS.

The argument sec_hostname is the name of the Secondary host as displayed in the output of the vradmin printrvg command.

Example:

To stop replication from the Primary RVG hr_rvg on seattle to the Secondary RVG on host london, type:

Changing the IP Addresses Used for Replication

You may need to change the host name or IP address of the Primary and Secondary used for replication if you move a Primary or Secondary to a new location or if you need to make the replication use a different network. You can change the host name or IP address even after replication has been established. The vradmin changeip command enables you to change the replication network between the Primary and a Secondary in an RDS.

Prerequisites for changing the IP addresses used for replication:

  The new host names must be configured for proper resolution at both the Primary and Secondary sites using the appropriate mechanisms such as DNS, NIS, or hosts. This means that each system must be configured to bring up their addresses on reboot, or if this is a cluster, the cluster monitor must bring up the proper address.

  The Secondary must be reachable from the Primary either through the previous network, the new network, or both the networks.

  If the previous network is no longer available, the vradmin changeip command must be run from the Primary host.

---

  Note    The VVR heartbeat port can be changed using the vrport command. To ensure that the RLINKs pick up the new port, always run the vradmin changeip command (without passing the newpri and newsec arguments) after changing the port. Restart the vxnetd daemon on the required system for the changes to take effect.

---

  To change the IP addresses used for replication

The argument diskgroup is the name of the local disk group that contains the RVG.

The local_rvgname argument is the name of the RVG on the host where the command is issued.

The sec_hostname is the name of the Secondary to which the replication network is being changed. This argument must be specified if the RDS has more than one Secondary.

The newpri attribute specifies a new hostname or IP address for the Primary host that is to be used to establish a network connection for the replication to the Secondary. This is the new value for the local_host attribute of the Primary RLINK and the remote_host attribute of the corresponding Secondary RLINK.

The newsec specifies a new hostname or IP address for the Secondary host that is to be used to establish a network connection for the replication. This is the new value for the remote_host attribute of the Primary RLINK and the local_host attribute of the Secondary RLINK.

Example:

This example shows how to change the network used for replication. The current configuration looks like this:

After making the changes to the replication network, the configuration looks like this:

  To change the IP addresses used for replication

1. From the Primary host seattle, issue the following command:
   # vradmin -g hrdg changeip hr_rvg newpri=seattle_hrnet \
   newsec=london_hrnet

   The vradmin changeip command changes the IP address of both the Primary RLINK and the corresponding Secondary RLINK to the new addresses newpri and newsec (in this example, seattle_hrnet and london_hrnet, respectively).

2. To verify the change on the Primary RLINK, issue the following command on the Primary host:
     # vxprint -l rlk_london_hr_rvg

   Output includes the following fields:

   
   Disk group: hrdg
   .
   .
   Rlink: rlk_london_hr_rvg
   .
   .
   remote_host=london_hrnet IP_addr=x.x.x.x
   .
   .
   local_host=seattle_hrnet IP_addr=x.x.x.x
   .
   .

   where x.x.x.x represents the corresponding IP address.

3. To verify the change on the Secondary RLINK, issue the following command on the Secondary host:
     # vxprint -l rlk_seattle_hr_rvg

   Output includes the following fields:

   
           Disk group: hrdg
   .
   .
   Rlink: rlk_seattle_hr_rvg
   .
   .
   remote_host=seattle_hrnet IP_addr=x.x.x.x
   .
   .
   local_host=london_hrnet IP_addr=x.x.x.x
   .
   .

   where x.x.x.x represents the corresponding IP address.

Changing the Network Ports Used for Replication

Port Numbers Used by VVR

VVR uses the UDP and TCP transport protocols to communicate between the Primary and Secondary. This section lists the default ports used by VVR. VVR uses the following ports by default when replicating data using UDP:

VVR uses the following ports by default when replicating data using TCP.

Displaying and Changing the Ports Used by VVR

Use the vrport(1M) command to display, change or set the port numbers used by VVR. You may have to change the port numbers in the following cases:

  To resolve a port number conflict with other applications.

  To configure VVR to work in your firewall environment.

  To configure VVR to work in your firewall environment when using UDP; to specify a restricted number of ports to replicate data between the Primary and the Secondary.

Port Used for Heartbeats

Use the vrport heartbeat command to display the port number used by VVR, for heartbeats. To change the heartbeat port number on a host, specify the port number with the vrport heartbeat command. Use the vradmin changeip command to update the RLINKs with the new port information, and then restart the vxnetd daemon on the required system for the changes to take effect.

  To display the port number used for heartbeats

  To change the port number used for heartbeats

Example

  To change the replication heartbeat port on seattle from 4145 to 5000

1. Use the vrport command to change the heartbeat port to 5000 on the required host.
     # vrport heartbeat 5000
2. Issue the vradmin changeip command without the newpri and newsec attributes.
     # vradmin –g hrdg changeip hr_rvg london
3. Verify the changes to the local RLINK by issuing the following command on the required host:
     # vxprint -g hrdg –l rlk_london_hr_rvg
4. Stop the vxnetd daemon.
     # /usr/sbin/vxnetd stop
5. Restart the vxnetd daemon.
     # /usr/sbin/vxnetd

Follow the same steps to change the heartbeat port on secondary (london).

Port Used by vradmind

To display the port number used by vradmind, use the vrport vradmind command. To change the vradmind port, specify the port number with the vrport vradmind command.

  To display the port number used by vradmind

  To change the port number used by vradmind

Port Used by in.vxrsyncd

To display the port numbers used by in.vxrsyncd, use the vrport vxrsyncd command. To change the port numbers used by in.vxrsyncd, specify the port number with the vrport vxrsyncd command.

  To display the port number used by in.vxrsyncd

  To change the port number used by in.vxrsyncd

Ports Used to Replicate Data Using UDP

To display the ports used to replicate data when using UDP, use the vrport data command. To change the ports used to replicate data when using UDP, specify the list of port numbers to use with the vrport data command.

Each RLINK requires one UDP port for replication. Specify an unused, reserved port number that is less than 32768 so that there is no port conflict with other applications. The number of ports specified must be equal to or greater than the number of RLINKs on the system.

  To display ports used to replicate data when using UDP

  To change ports used to replicate data when using UDP

For a system configured with one RLINK, use the following command:

For a system configured with multiple RLINKs, you can specify either a range of port numbers or a list of port numbers or both.

To specify a range of port numbers, use the following command:

For example: