SIRIS, ALTO, and NAS: Pairing a Target System for Agentless Backups



This article describes the process of protecting a target machine with Datto's agentless backup solution.


  • Datto SIRIS



This article assumes that your production machine meets the requirements described in the Getting Started with Agentless Backups article. Virtual machines that are not compatible with standard agentless backups will default to the more limited Universal VM Backup option. Universal VM Backup provides an alternative agentless method for protecting your machine.  

 Pairing a Target System for Agentless Backups

1. From the GUI of your Datto appliance, click the Protect tab. You will see the window shown in Figure 1.

Figure 1: Protect a System (click to enlarge)

2. Click AGENTLESS SYSTEM. You will see the window shown in Figure 2. The system will be listed on the left, and the operating system will be listed on the right. Note that operating systems that are not compatible with the standard agentless backup method will display [Universal VM Backup] next to the detected operating system and will use that method by default. See SIRIS, ALTO, and NAS: Universal VM Backups for more information.

figure2.pngFigure 2: VMware machines to protect (click to enlarge)

3. Check the boxes next to each target system that you want to back up. You can select multiple systems. If your VM is not listed, click the Add Hypervisor Wizard link to create a new hypervisor connection.

To virtualize an agentless backup, you must set up an iSCSI adapter on your ESXi host. See the article Connecting A Datto Appliance To A VMware Hypervisor for instructions.

4. The rest of the pairing process is the same as for agent-based systems. See the Protecting a System: Set Local Backup and Retention article for more information.

5. When the process is complete, you will see a Successfully Paired notification appear next to each selected system, as shown in Figure 3. You will also see a new entry for each agent on the Protect tab of the GUI when you click Return to Agent Overview.

Figure 3: Successful pairing (click to enlarge)

Backup Process

Before a Datto appliance can take an agentless backup, it must have a connection to your production hypervisor. For hypervisor connection steps, see the article Connecting A Datto Appliance To A VMware Hypervisor.

Unlike agent-based backups, which are VSS-dependent, in an agentless backup, the Datto appliance interacts directly with the hypervisor to snapshot and back up a virtual machine. It does so by taking the following steps:

  1. The Datto appliance uses the hypervisor connection to connect to the vSphere environment.
  2. It uses the VMware snapshot provider (part of VMware tools) to take a snapshot of the VM.
    The first two steps also occur when the Datto device pairs with the target VM.
  3. If the Datto appliance is a virtual device, it can use hotadd (through vddk-fuse) to directly attach the VMDK from the VMware snapshot to itself. By using hotadd, the backup data travels over the vSphere management network. As a failover, or if the Datto device is a physical appliance, it connects to the VMDK from the VMware snapshot using the Network Block Device (NBD) protocol. With this type of connection, the backup data transfers over the VM network.
  4. The Datto appliance uses libguestfs to analyze the disk image to get information about the disk structure and the file system(s) on it.
  5. The appliance transfers the backup data from the VMware snapshot of the VMDK to itself, and takes a ZFS snapshot of the disk images in the live dataset, just like an agent-based backup.

Figure 4 illustrates the data flow for the agentless backup process.

Figure 4: Agentless backup process (click to enlarge)

Additional Resources

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