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Replication: Continuous Replication with 2.11.2 and above

IN THIS ARTICLE

This article explains how you can use continuous replication with Qumulo Core 2.11.2 (and higher).

REQUIREMENTS

  • Source and target clusters running Qumulo Core 2.11.2 (or higher)
  • Administrative privileges for the clusters

IMPORTANT: Qumulo Core supports replication between different versions only if either the source or target cluster is running Qumulo Core 2.12.0 (or higher). For more information, see Replication: Version Requirements and Upgrade Recommendations.

DETAILS

Continuous replication takes a snapshot of the data in a directory on one cluster (source cluster) and transfers it to a directory on a different cluster (target cluster). While continuous replication runs, Qumulo Core scans modified files for any changed regions and sends only these changes to the target cluster; the job runtime remains proportional to the amount of data changes. By using snapshots, continuous replication generates a consistent point-in-time copy of the source directory on the target cluster. 

Configuring Privileges for Creating Replication Relationships

IMPORTANT: We don't recommend granting the following privileges to specific users. You should treat these privileges similarly to those that grant administrative access to your cluster. 

To create a replication relationship, the following privileges are necessary:

  • SOURCE_WRITE for the user on the source cluster to initiate the creation on the relationship
  • TARGET_WRITE for the user on the target cluster to authorize the relationship

Viewing the status of replication relationships requires the following privileges:

  • PRIVILEGE_REPLICATION_SOURCE_READ
  • PRIVILEGE_REPLICATION_TARGET_READ

Use special care when granting the following privileges to roles and users; these privileges grant access to functionality beyond replication relationship management.

  • PRIVILEGE_REPLICATION_SOURCE_WRITE grants permission to a user to access any data on a cluster, regardless of file or directory permissions that might restrict access otherwise. Because this privilege allows replication of any directory on the source cluster to another location, a user can potentially have permission to access data that is restricted on the source cluster.
  • PRIVILEGE_REPLICATION_TARGET_WRITE grants permission to a user to authorize replication relationships to any target directory on the cluster. This can potentially let a user authorize overwriting data that the user doesn't have permission to access through file or directory permissions.

To Create a Replication Relationship

  1. Log in to the Web UI and click Cluster > Replication.
  2. On the Replication Relationships page, click Create Relationship.
  3. On the Create Replication Relationship page, enter the following:
    1. Source Directory Path: The existing directory that you want to replicate.
    2. Target Directory Path: The existing directory to which you want to replicate.
    3. Target Address: One of the IP addresses from a node (we recommend a floating IP) on the target cluster.
    4. Port Number: You can click Default (3712) or enter a custom port.
      NOTE: If your enterprise firewall rules require this, you might have to configure a custom port.
  4. Click Add Blackout Window and then select the days and time when replication will suspend.
  5. (Optional) To add another blackout window, click Add Blackout Window.
    NOTE: You can add up to ten blackout windows. For more information, see Replication: Blackout Windows.
  6. To replicate files using locally-owned NFS IDs, under Map Local User/Group IDs to Associated NFS IDs (Qumulo Core 2.12.6 and higher), click Enabled. For more information, see Replication: NFS ID Mapping.
  7. Ensure that Enable Replication is checked.
  8. Click Save Relationship.

The relationship is available on the Replication Relationships page.

NOTE: A replication job doesn't begin until you authorize the relationship on the target cluster.

To Authorize a Replication Relationship

IMPORTANT: If your cluster is currently in a blackout window or if continuous replication for the replication relationship is disabled, replication doesn't begin. For more information, see Replication: Blackout Windows.

  1. Log on to the target cluster.
    A notification banner informing you of a new relationship authorization request appears.
  2. On the banner, click See details.
  3. On the Replication Relationships page, click Accept.

Viewing and Understanding Replication Relationships

On the source cluster, in the Web UI, click Cluster > Replication. On the Replication Relationships page, a list of source and target clusters appears.

The following table explains the icons that appear between the Source (n) and Target columns.

Icon Description
replication_running.png

Replication is running or is ready to run.

replication_waiting.png

Awaiting authorization from target cluster administrator.

replication_disconnected.png

The replication relationship is disconnected and the target directory is writable.

replication_blackout.png

The replication relationship is in a blackout window

replication_disabled.png

Continuous replication is disabled.

replication_reverting.png

Target directory is reverting to last recovery point before becoming writable.

replication_incomplete.png

The replication job is incomplete and will retry soon.

A progress bar in the Status column on the Replication Relationships page indicates the replication progress.

NOTE: The percentage isn't based only on the amount of data being replicated. It includes the number of files to be replicated and the amount of data to be transferred.

To review the throughput, run time, and data statistics of the current replication job in progress, click Details. Files that haven't changed since the previous replication job appear in the Unchanged column and aren't transferred.

To Edit a Replication Relationship

NOTE: You can't edit the source and target directory paths. To make these changes, you must create a new relationship.

  1. Log in to the Web UI  and click Cluster > Replication.
  2. On the Replication Relationships page, next to the relationship that you want to edit, click ellipsis.png > Edit Relationship...
  3. On the Edit Replication Relationship page, edit the settings (for more information, see To Create a Replication Relationship) and then click Save Relationship.

To Delete a Replication Relationship

  1. Log in to the Web UI  and click Cluster > Replication.
  2. On the Replication Relationships page, next to the relationship that you want to edit, click ellipsis.png > Delete Relationship...
  3. In the Delete relationship dialog box, review the source and target clusters and then click Yes, Delete.

Additional Considerations

  • Upgrades During Replication: Before you perform any Qumulo Core upgrades, you must wait until the replication job is complete. Upgrading Qumulo Core while a replication job is in progress causes the job to fail. When both clusters return to a state where replication is possible (the versions are the same), continuous replication can continue.
  • Continuous Replication: Depending on applications in use while a replication job runs, continuous replication increases the load on the cluster and can cause latency delays.
  • Reference Snapshots: At the beginning of a replication job, Qumulo Core creates a snapshot for each directory. At all times, Qumulo Core uses one reference snapshot for replication on the cluster. Administrators can view the snapshots used for replications and any other policy-based snapshots.
  • Snapshot Deletion: Qumulo Core takes a snapshot of directories on the target cluster. To ensure that a directory contains only the most recent snapshot, Qumulo Core deletes previous snapshots automatically.
  • Target Directory Permissions: When you create a replication relationship, Qumulo Core updates these permissions from read-write to read-only. When you delete the relationship, the permissions revert to read-write automatically.
  • Root Directories: Replication relationships that include the root directory of the target cluster are permitted only in Qumulo Core 2.12.0 (and higher).
    IMPORTANT: Including the root directory makes the entire target cluster read-only and might prohibit administrative functions such as upgrades. For more information, see Replication: Version Requirements and Upgrade Recommendations.
  • Local Users and Groups: Continuous replication doesn't support replicating local user or group information and fails when it encounters a file associated with local users or groups.
  • Maximum Number of Relationships: Qumulo Core supports up to 100 replication relationships.

RESOLUTION

You now know how to successfully configure and manage continuous replication in Qumulo Core 2.11.2 (and higher).

ADDITIONAL RESOURCES

Replication: Continuous Replication with 2.11.1 and below

Replication: Failover and Failback with 2.12.0 and above

Replication: Snapshot Policy Replication

Replication: Blackout Windows

QQ CLI: Replication

 

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