Zerto is a disaster recovery and replication platform for virtualised environments. It continuously replicates VMs from a protected site to a recovery site with minimal RPO (Recovery Point Objective).
Key components
| Component | Description |
|---|---|
| ZVM (Zerto Virtual Manager) | The management server for a site. One per vCenter |
| VRA (Virtual Replication Appliance) | Installed on each ESXi host. Handles the actual replication of VMs on that host |
| ZCM (Zerto Cloud Manager) | Manages cloud resources and ZORGs |
| VPG (Virtual Protection Group) | A group of VMs protected together as a unit |
| ZORG | A Zerto Organisation — a logical grouping of cloud resources |
| Journal | Stores changes to allow point-in-time recovery |
How replication works
- VRA intercepts writes at the hypervisor level
- Changes are sent to the recovery site VRA in near real-time
- A journal stores a history of changes (configurable retention)
- In a failover, the journal is used to roll VMs back to a specific point
Syncing types
- Bitmap sync — after an outage, marks exactly what changed and syncs only those blocks
- Delta sync — a deeper comparison between source and replica to verify consistency
Related Notes
- Zerto - Bitmap and Delta Syncing
- Zerto - VPG outside of ZORG
- Zerto - Generic Troubleshooting Part 2
- Zerto - Delete and Recreate VPG
- Zerto - Increase Journal Hard Limit