Bulk migration provides efficient low downtime migration. Unlike migration with vMotion migration, bulk migration requires a restart at the destination, the workload remains available during the replication process, and the switchover can be scheduled on a maintenance window. This allows large-scale migrations of hundreds (up to 250 in a single group) of workloads to VMware Cloud on AWS SDDC.
The bulk migration option is designed for moving large amounts of VMs in parallel. It does this by using host-based replicating, which allows workloads to stay online during the seeding/delta replication stages. After data replication has been completed, we have two options – either schedule the switchover for a specific maintenance window or switch over immediately to the target location. This happens over the HCX WAN optimized mesh and is backwardly compliant as far as vSphere 6.0. HCX also offers the option to upgrade VMTools and hardware compatibility in bulk migrations. This allows organizations with older versions of vSphere the opportunity to make these upgrades simultaneously.
Replication Assisted vMotion
Replication Assisted vMotion (RAV) combines the best of the vMotion and bulk migration capabilities to make migrating large numbers of live workloads easier. RAV uses bulk migration for the initial replication process and allows parallel operations and cutover scheduling. vMotion is used to finalize the migration of the delta data and VM memory and networking state for the zero-downtime migrations.
You will naturally choose RAV over bulk migration if your design includes an extension of VLANs and requires a workload to be accessible over a network for the whole duration of the migration process. Bear in mind that all the prerequisites for vMotion are still applicable.
The following figure illustrates the RAV migration process:
Figure 3.8 – A RAV migration process summary
Cloud to cloud
You can leverage HCX to not only migrate workloads from on-premises to VMware Cloud on AWS but also within a cloud, or between different clouds.
Within VMware Cloud on AWS, you can leverage HCX to migrate workloads between SDDCs deployed in the same region or different regions. For example, you can leverage HCX to move to the i4i host type from an i3-based SDDC. You would need to pay attention to the traffic flow and avoid ingress costs if possible.
Additionally, this feature can enable a multi-cloud migration from VMware Cloud on AWS to another hyperscaler’s VMware cloud infrastructure offering, such as Azure, GCP, or Oracle. The following figure shows a conceptual cloud-to-cloud migration between VMware on AWS and Azure VMware Solution (AVS), using HCX:
Figure 3.9 – The HCX multi-cloud migration option
HCX cloud-to-cloud migration is a great way to provide flexibility, choice, and control over multiple service offerings.