Volume Replicator 7.4.1 Administrator's Guide - Windows

To add a Secondary host

1. Select the Add Secondary option from the RDS right-click menu. On the Welcome panel click Next.

2. The Specify Secondary host for replication panel appears. Enter the name or IP address of the Secondary host in the Secondary Host field. Click Next. If the Secondary host is not connected to VEA, the wizard tries to connect it when you click Next. Wait till the connection process is complete and then click Next again.

   • If the disk group with the required data volumes and the Replicator Log volume as on the Primary host does not exist on the Secondary, Volume Replicator displays a message. Read the message, carefully.

     The option to automatically create the disk group, and the associated volumes on the Secondary host is available only if the required number of disks of the same type, having the same or a larger amount of space as that on the Primary is available on the Secondary. Otherwise, the RDS setup wizard enables you to create the required disk group and the volumes manually.

   • Click Yes to automatically create the disk group, data volumes, and the Replicator Log. When you click Yes any available disks are automatically chosen for creating the disk group on the Secondary host.

   • Click No to manually create the disk group with data volumes and the Replicator Log on the Secondary host. Complete the Create Dynamic Disk Group on Secondary host panel. If the Dynamic Disk group as on the Primary has already been created on the Secondary, then this panel does not appear.

   
   Complete the information on this panel as follows:

   Create cluster group	Choose this option only if you need to create clustered disk groups. Select the required disks from the Available disks pane. Either double-click on the host name or click the Add option to move the disks into the Selected disks pane. To select all the available disks, choose the Add All option.
   Create Dynamic Disk Group	Click Create Dynamic Disk Group to proceed with creating the Disk group. A disk group with the same name as that on the Primary is created.

   After the disk group has been created, click Next. The Volume Information on connected hosts panel appears.

   Complete this panel as described in step 3.

   If only a disk group without any data volumes or Replicator Log, as on the Primary host, exists on the Secondary, then Volume Replicator displays a message. Read the message, carefully.

   The option to automatically create the volumes on the Secondary host, is available only if the disks that are part of the disk group have either the same or a larger amount of space as that on the Primary or enough space to create volumes with the same layout as on the Primary.

   Otherwise, the RDS setup wizard enables you to create the required volumes manually.

   • Click Yes to automatically create the Secondary data volumes and the Replicator Log on the Secondary host. After the configuration has been automatically created on the Secondary, proceed to step 4.

   • Click No to create the Secondary data volumes and the Replicator Log manually, using the Volume Information on connected hosts panel. Complete this panel as described in step 3.

3. The Volume Information on connected hosts panel appears. This panel displays information about the availability of volumes on the Secondary nodes, if the Primary and Secondary hosts are connected to VEA.

   This panel does not appear if all the required volumes that are available on the Primary host, are also available on the Secondary hosts.

   • If the required disk group has been created but the data volumes and the Replicator Log have not been created on the Secondary host, then the panel displays the appropriate message against the volume name on the Secondary.

     Because the volumes have not been created the Create Volume option is enabled. Click this option to create the data volumes and the Replicator Log volume on the Secondary host.

   • The Create Volume panel automatically displays the volume name and the size after verifying the information about the Primary host. Complete the information on this panel as follows:

     Name	Displays the name for the volume. This is the same as that specified for the Primary volume.
     Size	Displays the size for the volume. This is the same as that specified for the Primary volume.
     Layout	Specify the volume layout. Select the appropriate option depending on your requirement.
     Disks Selection	Enables you to specify the disk selection method. You can select the following: Enable the Thin Provisioned Only check box to ensure that the Replicator Log volume is created only on Thin Provisioned (TP) disks. Note: Note: The check box remains disabled if the disk group does not have any TP disks. If this option is selected along with the Select disks automatically option, then the Replicator Log volume is created only on TP disks. However, if you enable this check box along with Select disks manually option, then the user can select only TP disks from Available Disks. For more information about Thin Provisioning refer to the Storage Foundation Administrator's Guide. Choose the Select disks automatically option if you want Volume Replicator to select the disks. Choose the Select disks manually option to use specific disks from the Available disks pane for creating the volumes. Either double-click on it or select the Add option to move the disks into the Selected disks pane.

     After verifying the information click OK to create the required volume. You are then taken back to the Volume Information on the connected hosts panel.

     Repeat the above steps for each of the volumes that has not been created, including the data volumes and Replicator Log.

   • After all the volumes have been created, the volume information panel is updated to display the available volumes on the Primary and Secondary host. Click Next.

   • If the required disk group and the volumes have been created but these volumes are not eligible for replication, then the reason for non-eligibility is indicated against the volume name.

     The Volume Information on connected hosts panel enables the appropriate option to convert a non-eligible volume to a Volume Replicator acceptable format.

     Complete the information on this panel as follows:

     Recreate Volume	This option is enabled if the required data volume is available on the Secondary, but is of a size greater than the Primary volume. Clicking this option displays a message that prompts you to confirm whether you want to recreate the volume. Choose Yes to recreate the volume using the Create Volume dialog. Note that this operation first deletes the volume resulting in the loss of the data that already exists on the volumes.
     Remove DRL	This option is enabled if the required data volume is available on the Secondary but has a DRL. Clicking this option displays a message that prompts you to confirm that you want to remove the log. Click Yes to confirm the removal of DRL.
     Remove DCM	This option is enabled if the required Replicator Log volume is available on the Secondary but has a DCM log. Clicking this option displays a message that prompts you to confirm if you want to remove the log. Click Yes to confirm the removal of DCM log.
     Expand Volume	This option is enabled if the required data volume is available on the Secondary but is of a smaller size than the Primary volume. Clicking this option displays a message that prompts you to confirm that you want to grow the volume. Click Yes to grow the volume to the required size.

     After you have converted the non-eligible volumes to a Volume Replicator acceptable format, click Next. The Edit replication settings panel appears.

     If the volume on the Secondary is already a part of another RDS, you cannot proceed. If you want to use the same volume, you must either remove the corresponding Primary volume from the Primary RVG or delete the other RDS.

4. Complete the Edit replication settings panel to specify basic and advanced replication settings for a Secondary, as follows:
   

   • To modify each of the default values listed on this panel, select the required value from the drop-down list for each property. If you do not want to modify basic properties, then the replication can be started with the default values when you click Next.

     Complete the following:

     Primary side IP	Displays the IP address on the Primary that is to be used for replication. If there is more than one IP address available for replication, you can choose the one that you want to use from the drop-down list. If the required IP address is not displayed in the list then edit the field to add the IP address.
     Secondary Side IP	Displays the IP address on the Secondary that is to be used for replication, if the Secondary is connected to VEA. If there is more than one IP address available for replication, you can choose the one that you want to use from the drop-down list. If the required IP address is not displayed in the list then edit the field to add the IP address. If you need to modify the IP addresses used for replication after creating the RDS, you can do it using the Change Replication Settings option.
     Replication Mode	Select the required mode of replication; Synchronous, Asynchronous, or Synchronous Override. The default is synchronous override.
     Replicator Log Protection	The AutoDCM is the default mode for the Replicator Log overflow protection when all the volumes in the Primary RVG have a DCM log. The DCM is enabled when the Replicator Log overflows.
     	The DCM option enables the Replicator Log protection for the Secondary host when the Replicator Log overflows, and the connection between the Primary and Secondary is lost. This option is available only if all the data volumes under the Primary RVG have a DCM Log associated with them.
     	The Off option disables Replicator Log Overflow protection.
     	The Override option enables log protection. If the Secondary node is still connected and the Replicator Log is about to overflow then the writes are stalled until a predetermined amount of space, that is, 5% or 20 MB (whichever is lesser) becomes available in the Replicator Log. If the Secondary becomes inactive due to disconnection or administrative action then Replicator Log protection is disabled, and the Replicator Log will overflow.
     	The Fail option enables log protection. If the log is about to overflow the writes are stalled until a predetermined amount of space, that is, 5% or 20 MB (whichever is lesser) becomes available in the Replicator Log. Note that the writes are stalled only as long as the Secondary is connected. If the connection between Primary and Secondary RVG is broken, then, any new writes to the Primary data volumes are failed.
     Primary RLINK Name	This option enables you to specify a Primary RLINK name of your choice. If you do not specify any name then Volume Replicator assigns a default name.
     Secondary RLINK Name	This option enables you to specify a Secondary RLINK name of your choice. If you do not specify any name then Volume Replicator assigns a default name.

     Click Next to start replication without any advanced settings.

     Proceed to step 5.

   • Click Advanced to specify the advanced replication settings.

     

     Complete the Advanced Replication Settings panel as follows:

     Latency Protection	By default, latency protection is set to Off. When this option is selected the High Mark Value and the Low Mark Value are disabled. Select the Fail or Override option to enable Latency protection. This Override option behaves like the Off option when the Secondary is disconnected and behaves like the Fail option when the Secondary is connected.
     High Mark Value	This option is enabled only when Latency Protection is set to Override or Fail. It specifies the maximum number of pending updates by which the Secondary can be behind the Primary. The default value is 10000, but you can specify the required limit. To ensure that latency protection is most effective the difference between the high and low mark values must not be very large.
     Low Mark Value	This option is enabled only when Latency Protection is set to Override or Fail. When the updates in the Replicator Log reach the High Mark Value, then the writes to the Primary continue to be stalled until the number of pending updates on the Replicator Log falls back to the Low Mark Value. The default value is 9950, but you can specify the required limit.
     Protocol	UDP/IP is the default replication protocol. Choose TCP/IP or UDP/IP for a regular Secondary. If the storage on the Bunker Secondary is directly accessible from the Primary use the STORAGE protocol, otherwise use TCP/IP or UDP/IP. Note: If the replication protocol for the Bunker Secondary has been set to STORAGE then you can change it only by deleting and recreating the Bunker with the required protocol; UDP/IP or TCP/IP. You cannot change the STORAGE protocol using the Change Replication Settings option.
     Packet Size(Bytes)	Default is 1400. Choose the required packet size from the drop-down list. The default unit for the packet size is Bytes. You can set the packet size only if the protocol is UDP/IP. Some firewalls do not support packet sizes greater than 1400 bytes. If you replicate across such a firewall, then use the default packet size to make sure all the Volume Replicator operations function as required. You can also set the packet size to 1300 by selecting from the list. The minimum packet size that you can specify is 1100 bytes. Note: If you need to set a value for packet size different from that provided in the list then you can do this by using the command line interface.
     Bandwidth	By default, Volume Replicator uses the maximum available bandwidth. To control the bandwidth that Volume Replicator replication uses, choose Specify Limit, and then enter the bandwidth limit in the field provided. The default unit is Megabits per second (Mbps) and the minimum allowed value is 1 Mbps.
     Enable Compression	Select this check box to enable compression for the Secondary host.

     After completing the Advanced Replication Settings panel, click OK. You are taken back to the Edit Replication Settings panel. Click Next. The Start Replication panel appears.

5. Choose the appropriate option from the Start Replication panel as described below:
   

   To add the Secondary and start replication immediately select Start Replication with one of the following options:

   Synchronize Automatically

   For an initial setup, then use this option to synchronize the Secondary and start replication. This is the default. When this option is selected, Volume Replicator by default performs intelligent synchronization to replicate only those blocks on a volume that the file system uses. If required, you can disable intelligent synchronization. Note: Intelligent synchronization is applicable only to volumes with the NTFS and ReFS file systems and not to raw volumes or volumes with FAT file systems.

   Synchronize from Checkpoint

   If you have considerable amount of data on the Primary data volumes then you may first want to synchronize the Secondary for existing data using the backup-restore method with checkpoint. After this completes use the Synchronize from Checkpoint option to start replication from checkpoint to synchronize the Secondary with the writes that happened when backup-restore was in progress.

   • To add the Secondary without starting replication unselect the Start Replication option. You can start replication later by using the Start Replication from the Secondary RVG right-click menu.

     Click Next to display the Summary panel.

6. Review the information on the Summary panel.

   Click Back to change any information that you had specified or click Finish to add the Secondary to the RDS and exit the wizard.