A migration wave is comprised of a group of workloads that will be migrated concurrently in a single migration event. There can be one or multiple miration waves in a single migration event. Migration events also contain other steps such as table-top activities, go/no-go checks, infrastructure updates (DNS, load balancers, etc), application teams testing, and operations hand-over.
The general recommendations for planning migration waves are as follows:
Plan migration waves around applications whenever possible. In other words, attempt to migrate all workloads of a given application in as few waves as possible. This approach helps to keep intra-application traffic local to the SDDC.
Plan to isolate larger/complex workloads to dedicated waves. Larger/complex workloads are typically databases or those VMs which have a high rate of I/O writes. These types of workloads tend to generate excessive amounts of delta data replication and may negatively impact other migrations.
Choose the most appropriate migration option which fits the needs of each workload group. If a workload can afford to be powered off, then use a cold migration. Bulk migration is the preferred migration method for most workloads. Most workloads can tolerate the relatively small amount of cutover time imposed by a bulk migration. Additionally, VMware HCX bulk migration provides the opportunity to perform certain updates such as VM machine version and vmtools upgrades; another benefit is that it keeps a shutdown copy at the source, so it can be restored quickly if needed.
Plan for contingency and recovery of the business activities even in the case some of the workload of the wave will have issue during the scheduled time.
Make sure the operations, monitoring, and backup teams are aware of the Migration Events and disable/suspend specific automated tasks (i.e. taking snapshots, starting filesystem backups, databases exports etc.) which will impact the migration.
Automate the initiation of migration waves. Often migration tools offer application programming interfaces (APIs) that allow writing scripts to batch the procedure. Automation not only simplify the migration activities but reduce the human errors.
