Major steps in ESX(i) Virtual Machine backup:
Connection to the host
When the backup is executed, the agent (Virtual Appliance or Windows Agent) connects to the ESX(i) host or vCenter server to perform the next step.
The agent (Virtual Appliance or Windows Agent) sends an API request to the ESX(i) host to create a snapshot with the following options:
- Snapshot the virtual machine's memory = off
- Quiesce guest file system = on
VMware Tools installed inside the guest OS performed the quiescing of the system and applications. At this point all operations are made by the ESX(i) host. Read this VMware KB article with detailed description of a VM snapshot. If the process fails on the VMware side, the API request returns error and this causes Acronis Backup for VMware (Acronis vmProtect) backup failure.
Metadata collection (in application-aware backup)
When the quiesce snapshot is triggered, VMware tools generate a file (e.g. vmNAME-vss_manifestsXXXX.zip) containing the backup components document (BCD) and writer manifests. This file is stored in the snapshot directory of the virtual machine. Acronis agent parses the manifest file and places it in the backup archive. For additional information, please refer to this link
Reconfiguration of the VM
LAN-free backup is activated automatically when available.
- In case of a Virtual Appliance (VA) it happens when it is deployed to the ESX(i) host, to which the datastore with the VM disks is attached. In case VA is connected to the vCenter, the linked clones of vdisks are attached. If VA is connected to the host, vdisks themselves are attached to the VA.
- For Windows Agent LAN-free backup is possible, when Agent is connected to the SAN storage with the virtual machines. Read this help topic about LAN-free backup in Agent for ESX(i) (Windows). In other cases vdisks are read via LAN.
VM data backup
The Agent reads the data from the virtual disks and VM configuration and writes it to the .tib file.
Links/disks are deleted from the Agent
After data is copied from the virtual disk and backup file is created, the link to the virtual disk or the virtual disk itself is deleted from the Agent.
After backup is finished and virtual disks were removed from the Agent, the snapshot should be consolidated. Agent sends the according API request to the ESX(i) host and the snapshot files are removed.
Remember that Acronis Backup for VMware (Acronis vmProtect) allows to run up to 5 simultaneous backup tasks by default. The virtual machines in the backup tasks are not limited, however they are backed up one by one.
See more about Acronis Backup for VMware (Acronis vmProtect) virtual machine backup in following articles:
Acronis vmProtect 9: Backing Up