Zerto Hypervisor-based Replication is made up of two components. The Zerto Virtual Manager (ZVM), and the Virtual Replication Appliance (VRA).
The ZVM, as the name suggests, is the manager of the solution, and it manages replication for the entire vSphere domain, keeping track of application data replicating in real time. From a scalability point of view, the ZVM can accommodate the replication management of 5000 VMs per vCenter.
The VRA is a module deployed on to physical hypervisor hosts as a VM made up of 2 vCPU's, and 4GB of RAM. The VRA is responsible for the continuous replication of data from selected virtual machines. It compresses and sends the data to the remote site over WAN links.
Each VRA can handle 1500 virtual disks. This architecture provides excellent scalability. As the number of VMs to replicate increases, you can meet the additional replication requirements by deploying additional VRA modules.
The use cases for Zerto mentioned were:
Recovery from ransomware - Zerto provides file-level recovery for all files when used as backup/business continuity. Zerto also keeps a journal history by a default of 24-hours. However, the recommendation is a journal of 96 hours. Any files infected with ransomware can be restored from the journal within the specified time window. The journal should not be used as a replacement for regular backups. It is a tool to use when the rapid recovery of data is needed.
Migration/replication between vSphere & Hyper-V and to Azure or AWS - great use case. Using an appliance deployed in Azure (Zerto Cloud Appliance), you can migrate your on-premise workloads to Azure using Zerto's continuous replication. You can also use Azure as a DR target for your on-premise ESXi or Hyper-V VMs.
If your requirement is to migrate to Azure, a migration license is available at a 1/4 of the cost of an enterprise license. It should be noted that a migration license is for one-time use only.
If you are interested in what Zerto has to offer, especially in the ever-growing hybrid cloud space, I recommend that you head over to zerto.com and request a trial license.