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Agentless vSphere protection is different than other Double-Take job types because it is reliant on ESXi technology. Instead of real-time replication, agentless vSphere protection takes snapshots of your source virtual machine and replicates those snapshots to the target host where they are applied to the target virtual machine. The following diagram illustrates a typical agentless vSphere protection job. In this example, the replication interval is 15 minutes. Additionally, the example accounts for taking point-in-time snapshots of the target virtual machine. The example point-in-time snapshot interval is one hour. The job is started at 8:00.
1. This is your first replication interval. It occurs between 8:00 and 8:15.
1.1. Double-Take takes a replication snapshot of the source virtual machine.
1.2. Double-Take checks to see if a scheduled point-in-time snapshot is due to run. Since this is your first replication interval and scheduled snapshots are enabled, a point-in-time snapshot of the target virtual machine will be triggered.
1.3. Double-Take replicates and applies the replication snapshot of the source virtual machine to the target virtual machine.
1.4. Double-Take takes a point-in-time snapshot of the target virtual machine.
1.5. Because the 15 minute replication interval has not been exhausted, Double-Take waits until the next replication interval is scheduled.
2. This is your second replication interval. It occurs between 8:15 and 8:35.
2.1. Again, Double-Take takes a replication snapshot of the source virtual machine.
2.2. Double-Take checks to see if a scheduled point-in-time snapshot is due to run. Because the point-in-time snapshot schedule of one hour has not elapsed, a point-in-time snapshot of the target virtual machine will not be triggered.
2.3. Double-Take replicates and applies the replication snapshot of the source virtual machine to the target virtual machine.
In this replication interval, the process took longer than the 15 minutes allocated, so there is no delay before the next replication interval starts. Double-Take logs a message when this occurs.
3. This is your third replication interval. It occurs between 8:35 and 8:50.
3.1. Double-Take takes a replication snapshot of the source virtual machine.
3.2. Double-Take checks to see if a scheduled point-in-time snapshot is due to run, but it is not time yet.
3.3. Double-Take replicates and applies the replication snapshot of the source virtual machine to the target virtual machine.
3.4. Double-Take waits until the next replication interval is scheduled.
4. This is your fourth replication interval. It occurs between 8:50 and 9:05.
4.1. Double-Take takes a replication snapshot of the source virtual machine.
4.2. Double-Take checks to see if a scheduled point-in-time snapshot is due to run, but it is not yet because it has only been 50 minutes since the job started.
4.3. Double-Take replicates and applies the replication snapshot of the source virtual machine to the target virtual machine.
4.4. Double-Take waits until the next replication interval is scheduled.
5. This is your fifth replication interval. It occurs between 9:05 and 9:20.
5.1. Double-Take takes a replication snapshot of the source virtual machine.
5.2. Double-Take checks to see if a scheduled point-in-time snapshot is due to run. At this point, it has been one hour since the job started, so a point-in-time snapshot of the target virtual machine will be triggered.
5.3. Double-Take replicates and applies the replication snapshot of the source virtual machine to the target virtual machine.
5.4. Double-Take takes a point-in-time snapshot of the target virtual machine.
5.5. Double-Take waits until the next replication interval is scheduled.
6. This is your sixth replication interval. It occurs between 9:20 and 10:25.
6.1. Double-Take takes a replication snapshot of the source virtual machine.
6.2. Double-Take checks to see if a scheduled point-in-time snapshot is due to run. There is not because it has not been one hour since the last point-in-time snapshot.
6.3. Double-Take replicates and applies the replication snapshot of the source virtual machine to the target virtual machine.
This replication interval took one hour and five minutes. Notice that the replication interval is set for every 15 minutes, but a new interval will not be started while a current interval is running.
7. This is your seventh replication interval. It occurs between 10:25 and 10:40.
7.1. Double-Take takes a replication snapshot of the source virtual machine.
7.2. Double-Take checks to see if a scheduled point-in-time snapshot is due to run. It has been one hour since the last point-in-time snapshot, so a new point-in-time snapshot of the target virtual machine will be triggered.
7.3. Double-Take replicates and applies the replication snapshot of the source virtual machine to the target virtual machine.
7.4. Double-Take takes a point-in-time snapshot of the target virtual machine.
7.5. Double-Take waits until the next replication interval is scheduled.