Adding object replication policies

Replication and Disaster Recovery Administration Guide for Hitachi NAS Platform
Version
14.7.x
14.6.x
Audience
anonymous
Part Number
MK-92HNAS009-26

The Add Object Replication Policy pages allow you to define the properties of a new object replication policy, including its source file system and its replication target (server/cluster, EVS, and file system).

If this is the first policy created, and if the file system is not configured to transfer access points with a replication, then the option to manually configure the file system to transfer access points will be given. You are provided with more resolution options on the second Add Object Replication Policy page.

Note: Selecting a source or target file system that already has an object replication policy defined will not cause the old policy (or policies) to be overwritten. You can have multiple replication policies on a source file system, each pointing to a different target file system. You could also have multiple policies with a single source/target pair; however, it is not recommended.
  1. Navigate to Home > Object Replication to display the Object Replication page.
  2. In the Policies section, click add to display the Add Object Replication Policy page.
    CAUTION:
    If the file system is not configured to transfer access points with replications, and if the target file system must later be recovered as a read-write file system (for example, to replace the source file system in a disaster recovery situation), the shares and exports configured on the source file system are not copied to the target file system. Network clients that relied on those shares and exports to access their data on the source file system are longer able to access the recovered data on the target file system. The shares and exports must be individually configured to be transferred with replications, via their respective share and export details pages, in order to allow network clients to access their data on the source file system. You are provided with more resolution options on the next page, after clicking next.
    Note: It is recommended that the replication target is at least as big as the source file system, to ensure that all data can be replicated on the target. This is especially important if you intend to keep multiple snapshots on the target, as they require more storage space.
    Field/Item Description
    Identification
    Name The name of the object replication policy.
    Source
    EVS/file system The name of the source EVS and file system that is to be replicated to the object replication target. To change the source EVS/file system, click change….
    EVS IP Address The default value for this field is 'Automatically selected'. If required, select the IP address for the source EVS from the list.
    Target
    Server Select a server from the list to be the target of the object replication policy. After selecting a server, click select a target... to select an EVS and file system. For managed servers, the EVS Name and File System fields are automatically populated when you select a file system using select a target... Or, alternatively, type the EVS IP/host name and file system name in the corresponding fields.
    EVS DNS Name or IP Select the EVS IP/host name in this field.
    EVS IP Address Enter the EVS IP address in this field.
    File System Select the target file system of the object replication policy. If the replication process is not managing the server on which the target file system is hosted, or if the destination file system does not yet exist, select Specify EVS IP/host name and file system from the list and type the details in the appropriate fields.
    Note: The replication target file system should be at least as large as the source file system to ensure that all data can be replicated on the target. If you intend to keep multiple snapshots on the target, it is especially important that the target be larger than the source, because the additional snapshots on the target file system will require storage space.
    Note: The tiering of both the replication source and target file systems must agree; you cannot have a tiered source file system replicated to an untiered file system, and you cannot have an untiered source file system replicated to a tiered file system.
    Object Replication Listening Port The port on which the destination server is listening. The default is 59550. The port on which the destination server listens is configured on the Object Replication Configuration page of the NAS Manager, or through the replication-listening-port CLI command.
    Note: To change the listening port for the target server, you must make that server the currently managed server of the replication process, then use the Object Replication Configuration page of the NAS Manager to change the listening port.
  3. Specify the details for the policy identification, replication source and the replication target.
  4. Click next to continue with the policy configuration.
    The replication process checks if the source file system is configured to allow the access points (SMB shares and NFS exports) on it to transfer with the object replication. If it is not, a NAS Manager page is displayed that gives you the option of configuring the source file system so it can transfer shares and exports with the replication. If another policy already exists for this file system, the check for access point transferability is skipped, and the second part of the Add Object Replication Policy page is displayed:

    The policy can result in two types of replications of the source file system: an initial replication, and an incremental replication. A replication of an initial snapshot results in a full copy of the source file system being replicated on the target, while subsequent replications use an incremental snapshot that only copies objects that have changed since the initial snapshot was taken.

    When setting snapshot rules, you can choose either an automatic snapshot rule or an existing, named rule.

    In order to avoid snapshots being taken of inconsistent data, please carefully note the following recommendations:
    • If you choose the automatic snapshot rule option, the snapshot is taken whenever the replication first runs. In order for the replication engine to take a snapshot with consistent data (that is, data that is not actively being modified on the source file system), it is recommended that the replication be run when the file system is not being actively accessed. For example, the replication can be run manually, when the source file system is inactive, to obtain a snapshot with consistent data. Or, the replication policy should be scheduled to run when the file system is not being accessed.
    • If you choose a named snapshot rule, the snapshot is taken when specified by the rule; however, it is recommended that the snapshot is taken manually, when the file system is not being actively accessed, or scheduled to be taken when such a time is anticipated. Then the replication should be scheduled at a time when the server is minimally active, or run manually at such a time.

    The following table describes the fields on the second Add Object Replication Policy page:

    Note: If a database application is writing to its database when a snapshot is taken, the snapshot can contain only some of the writes to the database, rather than all of them. In such a case, the database might contain only partially written records and is therefore not consistent.
    CAUTION:
    Setting the snapshot options for the source and target file systems must be done very carefully, to ensure that replications provide a good copy of the data on the target. It is recommended that you consult with support representative if you are unsure of how to correctly set snapshot options for an object replication.
    Field/Item Description
    Source File System Options for taking snapshots of the source file system:
    • Snapshot source file system using automatic snapshot rule, which allows the replication to use its default snapshot rule to take and manage snapshots.
      Note: If you choose this option, each incremental snapshot is deleted when the next replication runs. Therefore, because the snapshot queue only contains one snapshot, it is recommended that replications are not scheduled too closely together in order to prevent an existing snapshot from being removed before the next replication starts.
    • Use snapshot rule, which means that the source snapshot retention policy can be customized to retain a different number of snapshots on the source file system.
      Note: If you choose this option, set the schedule for the snapshot rule so a snapshot is created before the replication runs, to ensure that a new snapshot is available for the replication. A snapshot of the source file system is only taken if the replication policy is configured to use an automatic snapshot rule. If it is using a named rule, the replication will use the latest snapshot created by that rule; it does not take one automatically.
    Target File System Options for taking snapshots of the target file system:
    • Snapshot target file system using automatic snapshot rule, which allows the replication to use its default snapshot rule to take and manage snapshots on the object replication target.
    • Use snapshot rule, which allows the snapshot retention policy to be customized to retain a different number of snapshots on the source and destination.
  5. Enter the processing options.
  6. Click next to advance to the Add Object Replication Policy page.
    Note: The source and target file systems are evaluated and, if any issues are detected, a page appears listing them and offering options to help you either correct the issue or to go back to the previous page.
  7. Review policy settings, and then click create.
  8. To add a schedule for this policy, click yes to display the Add Object Replication Schedule page.