Recovery
In the Recovery page, you can recover data by performing a failover for your iSCSI LUN to one of the destinations.
When the source of a replication task fails to deliver normal services, you can perform recovery by failing over the iSCSI LUNs to the destination. When you perform a failover, the replicated iSCSI LUNs will change the status from read-only to writable on the original destination, taking over the workload of the original source. You can redirect all of your clients and applications to access the new hostname/IP address of the original destination. After the original source resumes normal operations, you can re-protect your iSCSI LUNs. Before you perform the re-protect operation, all replication tasks between the source and destination will be paused. When both the source and destination work normally, you can perform a switchover for your replication task to exchange their roles to meet your need of data storage.
To ensure successful recovery of your services, applications and iSCSI LUNs, you can perform a test failover to clone a writable iSCSI LUN on the destination (as the simulated new source) where you can conduct essential tests to check if this clone works well. For example, you can test if the virtual machines hosted by the tested iSCSI LUN can successfully launch their operating system.
iSCSI LUN
For the best user experience, it is recommended to install the same version of Snapshot Replication on your source server and destination server.
To restore an iSCSI LUN:
- Select the iSCSI LUN you wish to restore.
- Click Recover.
- Select the snapshot version you wish to restore from.
- Click Action, and select Restore in-place from the drop-down list.
- You will see a confirmation message. Click Yes to confirm the action.
To clone a snapshot to a new iSCSI LUN:
- Select the iSCSI LUN you wish to clone.
- Click Recover.
- Select the snapshot version you wish to clone to a new iSCSI LUN.
- Click Action, and select Clone with a new name from the drop-down list.
- You will be redirected to the Clone page in iSCSI Manager > Snapshot > Clone. Enter the name of the cloned iSCSI LUN and click OK to finish.
Note:
- Restoring and cloning iSCSI LUNs are not available when a volume has less than 1GB of free space.
- If a snapshot is taken when transfer of any files is still in progress, the data consistency will not be guaranteed.
- The snapshots of the iSCSI LUNs used by Cinder cannot be restored in-place. You can only Clone with a new name for such snapshots, and they will be cloned to general Advanced LUNs after the operation. For more information and for DSM versions earlier than DSM 6.2, please refer to Synology Unified Controller Help > iSCSI Manager > LUN.
- If an iSCSI LUN is used as the destination of replication, it cannot be restored by using Restore in-place.
To switch over the replication of iSCSI LUN:
- Select the replicated iSCSI LUN you wish to switch over.
- Click Action > Switchover.
- Select the new destination if there are multiple replication tasks of the iSCSI LUN.
- Click Switchover to start the action.
Note:
- The volume where the iSCSI LUN is located must have more than 1GB of free space if you wish to switch over the replication.
To fail over a replication of iSCSI LUN:
- Select the replicated iSCSI LUN you wish to fail over on the destination.
- Click Action > Failover.
- Select the version of snapshot to restore.
- Click Failover to start the action.
Note:
- You can only initiate a failover upon failure of the source.
To perform a forced failover for a replication of iSCSI LUN:
- Select the replicated iSCSI LUN for which you wish to perform a forced failover on the destination.
- Click Action > Force Failover.
- Select the version of snapshot to restore.
- Click Force Failover to start the action.
Note:
- You run the risk of data loss when initiating a forced failover.
To re-protect the replication of an iSCSI LUN:
When being failed over to the destination, the replication task will stop syncing data between the source and destination. You will need to re-protect the replication task after the original source is recovered.
- Select the failed over iSCSI LUN you wish to re-protect.
- Click Action > Re-protect.
- Select the new source.
- Select the new destination if there are multiple replication tasks of the iSCSI LUN.
- Select to re-protect with the data on either source or destination.
- Tick the Sync immediately after operation checkbox if you want to sync immediately.
- Click Re-protect to start the action.
Note:
- The data of the replicated iSCSI LUN existing on the new destination will be overwritten by that on the new source.
To perform a test failover for a replicated iSCSI LUN:
- Select the replicated iSCSI LUN you wish to test.
- Click Action > Test Failover.
- Select the Test Server if there are multiple replication tasks of the iSCSI LUN.
- Enter the Name for Test Failover of the iSCSI LUN, and select a snapshot version to test.
- Click Test Failover to start the action.
Note:
- Performing a switchover/failover of a replication will clean up its test failover.
- You cannot create a replication task for a test failover iSCSI LUN.
To clean up test failover for a replicated iSCSI LUN:
- Select the replicated iSCSI LUN of which you wish to clean up test failover.
- Click Action > Cleanup Test Failover.
- Tick the checkbox for the test failover if you wish to keep the iSCSI LUN created for the test failover.
- Click Cleanup Test Failover to start the action.