HCX vs vMotion: Choosing a Tool for Cross-vCenter Moves

Moving VMs between vCenters or data centers, you have two VMware-native options: vMotion (including cross-vCenter vMotion and Advanced Cross vCenter vMotion in the vSphere Client) and HCX, which is included in VMware Cloud Foundation. Both can move a running VM. The choice comes down to the network between the sites, how many VMs you're moving, and whether the VMs have to keep their IP addresses.

Our first question is always the link: the bandwidth and latency between the vCenters or sites. On a fast, low-latency link, plain vMotion usually does the job. When the link is slow, long or shared with production traffic, HCX's replication-based migration and WAN optimization earn their setup time.

What cross-vCenter vMotion needs

• Layer 3 connectivity for vMotion and management between the source and target hosts, with enough bandwidth and latency within VMware's supported limits for long-distance vMotion: up to 150 ms round trip, and at least 250 Mbps for each concurrent vMotion.
• Compatible CPUs (or EVC) and a network and datastore at the destination for each VM.
• The target network must already exist; vMotion doesn't stretch layer 2, so VMs keep their IP only if the same subnet is reachable at the target.
• Best for: small numbers of VMs, same-site vCenter consolidation, and moves on a fast, low-latency link.

What HCX adds

• Network Extension: stretches layer 2 segments to the target site so VMs keep their IP addresses and you can move in waves before re-routing.
• Bulk Migration: replication-based, scheduled cutover of many VMs at once, with a short reboot at switchover.
• HCX vMotion and Replication Assisted vMotion (RAV): live moves, and live moves of larger groups with replication doing most of the work in advance.
• WAN optimization and its own interconnect appliances, which helps over slower or longer links.
• Mixed versions: HCX can move workloads from older vSphere versions to newer ones (check the current HCX interoperability matrix).

Side by side

When to choose which

• Choose vMotion when the link is fast with low latency, the target network exists and the VM count is small.
• Choose HCX for data center exits, cloud moves (such as Azure VMware Solution), re-IP avoidance and wave-based migrations.
• Many migrations use both: HCX for the bulk of the estate and plain vMotion for stragglers.

Gotchas

• Plan the removal of HCX network extensions: routing has to move to the target before you unstretch.
• Watch for VMs with RDMs, passthrough devices or attached ISOs, which block or complicate moves.
• Size the HCX appliances and interconnect for the wave, not the average day.