New replications perform a complete initial synchronization, copying the entire source data from the workload - vApp or virtual machine (VM) to a datastore in the destination site. Using replication seed lowers the network data traffic and the required time for the initial synchronization of the replication while briefly consuming double storage space.
Due to the size of the workload or to the network bandwidth, a full initial synchronization might take a long time. To reduce the initial synchronization time, transfer the source workload to the destination site by using removable media, failover of a previous replication, or other means of data transfer. Then, in the destination site, configure replication by using the vApp copy or the VM copy as seed.
- In the destination site VMware Cloud Director Availability stores the replication data without creating copies of the seed workload.
- One seed vApp or VM allows configuring only one replication.
- Seed can be configured only when creating a new replication.
Destination Datastore Space Consumption
To be able to create the independent disk for the replication, when starting a replication requires at least as much space as the source workload capacity in a single compliant destination datastore.
To start a replication using seed requires twice the same storage space. The double space requirement lasts for a short period of time between the independent disk creation and the removal of the seed. Using a seed lowers the network traffic, not the datastore usage, and requires as much free space, as for replicating from scratch, even though the space is only briefly reserved and might not even get fully utilized.
After VMware Cloud Director Availability collects the storage consumption and updates the independent disk, the disk usage with the respective quota reservation might shrink. Shrinking is due to reporting the actual usage, instead of the total disk capacity.
Use a VM as a Replication Seed
To use a VM as a seed, in the destination site, select a VM that has an identical disk configuration with the seed VM. The size and number of disks, and their assignment to disk controllers and bus nodes must match between the replication source and the seed VM.
For example, if a replication source VM has two 4 GB disks, one of them assigned to SCSI controller 0 at bus number 0, the second one to SCSI controller 1 at bus number 2. Your seed VM must have the same hardware configuration - two 4 GB disks, at SCSI 0:0 and at SCSI 1:2.
The disks in the source virtual machine must match the disks in the seed VM. Else the reverse replication fails with a Disks of provided seed VM don't match the disks of the source VM message. For more information, see Excluding disks from replicating.
Use a vApp as the Replication Seed
To use a vApp as a seed, in the destination site, select a vApp that has an identical VM set with the seed vApp. The VMs in the seed vApp must have a matching name to the VMs in the source site vApp. Each VM in the seed vApp, must meet the prerequisites to be a seed VM of the VM with the same name in the source site.
After you start a vApp replication, in the VMware Cloud Director™ inventory, the seed vApp is empty and you can manually copy the vApp settings and metadata that did not replicate from the source site. The seed vApp remains available as an empty copy and you can remove it at your discretion.
Create a Replication Seed
Use one of the following methods for creating a seed in the destination site.
