This article describes the function of the Create Rescue Agent option for Datto appliances capable of running local virtualizations.
When starting a local virtualization, you have the option to create a virtual Rescue Agent from the selected snapshot of the Source Agent and take crash-consistent backups of the VM. The feature creates a new backup agent on the Protect tab of the Datto appliance's GUI, and writes all of the Source Agent's configurations and data changes to automatic incremental snapshots. The agent will continue to back itself up until you restore the production machine or its replacement. This ensures that whenever you want to bring the original machine back into service, your data is ready and waiting.
Because the Rescue Agent creates a 'forked' backup set from the Source Agent's snapshots, the only additional space the Rescue Agent will use on your appliance will come from its incremental backups.
1. To create a virtualization with a Rescue Agent, start a local virtualization. In the Local Options screen, configure the virtualization, and check the Create Rescue Agent box, as shown in Figure 1.
2. Click Apply, followed by Start VM. You will be prompted to choose whether or not you would like to pause backups on the protected machine. Depending on your recovery scenario, click either Pause Backups or Continue Backups, and then click Confirm.
Figure 2: Pause or continue backups
3. Your virtualization will mount and begin running in the Local Virtualization screen. On the Protect tab of the Datto appliance GUI, you will see a new agent with a name comprised of the word 'rescue' and the protected server's IP address or FQDN, as shown in Figure 3. This is the Rescue Agent for your running virtualization. You can manage this agent the same way you would manage any other agent, including setting a custom backup schedule for it through the Configure Agent Settings page.
4. If the Source Agent that you created the Rescue Agent from is encrypted by the Datto appliance, the Rescue Agent will also be created as an encrypted agent. It will use the same encryption password as the Source Agent, and you will need to unseal the agent on the Protect tab of the appliance GUI in the event of a device reboot.
If you were running a virtualization of the Rescue Agent at the time of the device reboot, you will also need to unseal and restart the virtualization from the Restore tab.
Examples of a sealed Rescue Agent are shown in Figures 4 and 5.
Figure 5: Sealed rescue agent, Restore tab
5. When you no longer need the Rescue Agent, remove the protected virtualization from the Restore tab of the Datto appliance GUI by clicking Stop and then Archive.
6. When you click Archive, your Datto appliance will archive the Rescue Agent's dataset, as shown in Figure 7. This will hide the Rescue Agent in the list of Restores, stop all backups, and unmount the VM permanently. Only use this option if you have no need to initiate backups of this Rescue Agent in the future.
Figure 7: Stop and archive
7. When you no longer need the Rescue Agent's dataset, you can remove it by clicking Remove Rescue Agent on the Protect tab of the Datto device GUI. This will permanently delete any backups taken by the Rescue Agent while it was running.
Q: Are Rescue Agents subject to retention rules? Will I be alerted if a Rescue Agent uses too much of my Datto device's free disk space?
A: Rescue Agents are subject to the same retention rules as conventional agents. They will trigger device alerts in the same way that conventional agents do.
Q: Does a Rescue Agent need to take a full backup to create its dataset?
A: Rescue Agents don't require a full backup because of how the Datto appliance leverages ZFS (through a ZFS promote). Rescue Agents are no more likely to cause disk space issues than the original agent was.
Q: Does the Rescue Agent continue to back up if the Datto device is critically low on space, or will it check to see if the device has 30GB or less of free space before taking the snapshot?
A: The Rescue Agent will check to ensure that appropriate space is available on the Datto appliance before it runs a backup.
Q: If a Source Agent is encrypted, will the Rescue Agent be encrypted?
A: Yes, if the Source Agent is encrypted, the Rescue Agent will use the same encryption settings.
Q: Do Rescue Agents replicate their backups to the Datto Cloud?
A: Yes, Rescue Agents can replicate offsite.
Q: Does the Rescue Agent needs to sync a full base offsite before normal offsite sync begins, despite it not needing a full backup to start running?
A: Currently a Rescue Agent will send a full base offsite - this is because, while the Rescue Agent can reference the data of its Source Agent locally, when it replicates offsite, it requires a full dataset to be able to restore in the cloud.