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NetBackup Instant Recovery for VMware is a feature of Symantec's NetBackup enterprise backup software platform. The feature allows users to boot an instance of a virtual machine (VM) directly from a backup copy, allowing them to run an application directly from secondary storage in the event of an outage while the primary VM is being restored. According to Symantec, the startup time depends on the network speed and storage speed, not on the size of the VM.
This capability is often referred to generically as instant recovery or recovery in place. It has emerged in the past few years as a way to meet the demands of organizations with very low recovery time objectives. A number of backup software products, such as Commvault Data Platform (formerly Simpana), Veeam Backup & Replication, and EMC Avamar offer similar capabilities.
How instant recovery works
Most products offering instant recovery features work in a similar manner. Instant recovery is made possible by disk-based backups and by a hypervisor's ability to create VM snapshots. When a backup administrator performs an instant recovery, a virtual machine is mounted directly from the backup copy on secondary storage. Once the VM is mounted, a hypervisor snapshot is created. This allows the backup copy of the VM to remain unmodified because all write operations are directed to a differencing disk. Once this differencing disk is in place, network traffic for the VM is redirected to the backup copy of the VM. Now that the VM is available on the network, the administrative staff can work on performing a restoration. Once the restore is completed, the contents of the differencing disk are merged with the newly recovered VM and user traffic is redirected back to the primary copy of the VM.
In NetBackup, instant recovery is initiated by an administrator who runs a command to access the VM from its backup image. NetBackup mounts the image as an NFS data store, creates a temporary data store on the ESX host where the VM will be restored, and creates a snapshot of the VM. New write requests go to the temporary data store, while the NFS data store is read-only. Storage vMotion is then used to copy the VM data from the NFS data store to the temporary data store. VSphere Client is used to consolidate the VM's snapshot files. At that point, users run another command to unmount the NFS data store.
Although instant recovery is usually regarded as a disaster recovery (DR) feature, it can be used for DR testing and to create development/test environments. Some administrators even use instant recovery to create temporary copies of VMs that can be used to test operating system patches.
While NetBackup Instant Recovery for VMware is an important advancement, you must decide whether your backup server has enough power to run one or more applications as the restore process occurs. Otherwise, application performance may be inadequate.
These restores require manual intervention and it will take approximately 15 minutes to perform a NetBackup Instant Recovery for VMware -- faster than a traditional restore, but not a zero-downtime approach.
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