The OS Assisted Migration (OSAM) service includes several components that work together for connecting and forwarding guest workloads in the source environment.

Refer to the following considerations when deploying and operating OS Assisted Migration in your environment.

  • The OSAM service converts non-vSphere guests to vSphere virtual machines. This conversion process involves halting OS services to quiesce the guest virtual machine. The downtime for this conversion process can vary from minutes to hours depending on a virtual machine size and activity.

  • OSAM migrations require a guest network configuration in the HCX Compute Profile.

  • The HCX Sentinel agent software encrypts all connections to the Sentinel Gateway. The encryption cannot be deactivated.

  • The HCX Sentinel appliance must be deployed in a vSphere environment, and not within KVM or Hyper-V.

  • To use HCX Network Extension with OSAM deployments, VLANs in the non-vSphere environment must also exist on the source vSphere environment network switches and in vCenter Server as Distributed Port Groups.

  • For vSphere-based site pairs, each Service Mesh deploys one Sentinel Gateway (SGW) and its peer Sentinel Data Receiver (SDR), and supports up to 50 active replica disks.

  • For non-vSphere site pairs, the Service Mesh deploys one Sentinel Resource Gateway (SRG) that supports up to 50 active replica disks.

  • HCX OSAM deployments support 200 concurrent VM disk migrations across a four Service Mesh scale out deployment. In this Service Mesh scale out model for OSAM, the HCX Sentinel download operation is presented per Service Mesh.

  • Guest virtual machines can only be migrated to a datastore that is accessible by the SDR or SRG appliance.
  • Redeployment of Sentinel appliances is not allowed when any migration is in-progress.
  • Only "thin" and "thick" disk provisioning types are supported as the disk provision type for the migrated system. The "Same as Source" option is not supported.
  • OSAM Migration using PowerCLI:
    • PowerCLI 11.5 is not supported.
    • Migrations with VMware Cloud Director as target are not supported using PowerCLI.
    • Mobility Group migration is not supported through PowerCLI for VMware Cloud Director (all services).
  • The OSAM migration service applies the default storage policy to the migrated VMs and their disks. Currently, the OSAM service does not support a user-selected storage policy.
  • Changes to source Guest virtual machine configurations while a migration is in progress might not take effect in migrated virtual machines and sometimes might lead to migration failure.
  • VMs with Linux GuestOS can have up to 15 hard disks attached.
  • VMs with Windows GuestOS can have up to 64 volumes or file-systems.

For information regarding migration limits, search for VMware HCX in the VMware Configurations Maximums tool.