Zerto Virtual Replication enables protecting virtual machines, for both disaster recovery or for extended, longer term recovery from a retention repository, by protecting the relevant virtual machines in virtual protection groups. A virtual protection group (VPG) is a group comprised of virtual machines that are grouped together for recovery purposes. For example, the virtual machines that comprise an application like Microsoft Exchange, where one virtual machine is used for the software, one for the database, and a third for the Web Server require that all three virtual machines be replicated to maintain data integrity.

Once a VPG has been created, each virtual machine in the VPG can be replicated on the recovery site under the VRA on the host specified in the VPG definition as the host for the recovery of the virtual machine.

The following are described in this section:

Disaster recovery using Zerto Virtual Replication enables recovering from a disaster to any point between the moment just before the disaster and a specified amount of time in the past up to 30 days. The recovery is done in real time at the recovery site with a minimal RTO.

Virtual machines are protected in VPGs. Once a VPG is created, Zerto Virtual Replication creates a copy under the management of a Virtual Replication Appliance, VRA, on the recovery site, of the protected virtual machine files, such as the configuration and data files. A VRA is installed on every host where the machines are to be recovered.

When a recovery operation is performed, the VRA creates the virtual machines defined in the VPG and attaches the virtual disks to these machines. It then promotes the data from the journal to the virtual machine disks.

Every write to the protected virtual machine in a VPG is copied by the VRA on the same host as the protected machine and passed to the VRA on the host in the recovery site. The VRA on the host in the recovery site was specified in the VPG definition as the host for the recovery of the virtual machine. These writes first are saved in a journal for a specified period, and then moved to replica virtual disks managed by the VRA, which mirror the protected virtual machine disks.

After initializing the VPG, all writes to the protected virtual machines are sent by the VRA on the relevant host for each virtual machine on the protected site to the VRA on the recovery site specified as the recovery host for the virtual machine. The information is saved in the journal for the virtual machine with a timestamp, ensuring write-fidelity. Every few seconds the Zerto Virtual Manager causes a checkpoint to be written to every journal on the recovery site for every virtual machine in the VPG, ensuring crash-consistency.

The data remains in the journal until the time specified for the journal when it is moved to the relevant mirror disks, also managed by the VRA for the virtual machine. In this way, you can recover the virtual machines using the mirror disks and then promoting the data from the journal to include the final few hours of data for each virtual machine. For more details about the journal, see “The Role of the Journal During Protection”, on page 30.

 

When testing that the recovery works as planned, the VRA creates the virtual machines defined in the VPG and uses scratch disks to simulate the virtual machine disks for the duration of the test. This enables the ongoing protection of the virtual machines and the possibility of a failover if required during the test.

To recover files and folders, see “Recovering Files and Folders”, on page 308.

If you need to extend the recovery ability to more than the 30 days that are available with disaster recovery, Zerto Virtual Replication provides Long Term Retention that enables saving the protected VPGs for up to one year in a state where they can easily be deployed.

During the retention process, data from the recovery VPGs is saved in a repository as repository sets that can extend as far back as a year. These repository sets are fixed points saved either daily, weekly or monthly.

When a Retention process starts, the DSS communicates with the VRA on the recovery site to create the retention sets of the VPGs, and saves these sets in the repository.

To set up Long Term Retention to protect VPGs, see “Using Zerto’s Long Term Retention”, on page 316. Configuring Long Term Retention is part of defining a VPG.

After initializing the VPG, Zerto Virtual Replication periodically checks that the time to run a Retention process has not passed. At the scheduled Retention process time, the Retention Process is run and the retention set is stored in the specified repository.

Retention sets are kept for the retention period specified in the VPG’s Retention Policy. Over time the number of stored retention sets are reduced to save space.

To restore VPGs, see “Using Zerto’s Long Term Retention”, on page 316.