Live migration of a VM between hosts fails or is very slow.
Live migration requires network, CPU compatibility and authentication to align. Failures usually trace to CPU feature differences, missing constrained delegation, or a slow migration NIC.
Try this first
- 1Check CPU compatibility: in Hyper-V Manager, VM properties, Processor, Compatibility, tick 'Migrate to a physical computer with a different processor version' before live migrating.
- 2In VMware: Enhanced vMotion Compatibility (EVC) at cluster level, set to the lowest CPU generation in the cluster.
- 3Authentication: Hyper-V live migration via Kerberos needs constrained delegation in AD on the computer object. CredSSP works too but is less secure.
- 4Network: a dedicated 10G+ NIC for live migration, not over the management NIC. Otherwise management traffic floods and migration takes minutes.
- 5Test with a small VM, watch the transfer. 'Memory still being migrated' should drop steadily, not bounce forever on a busy workload.
When to bring us in
For VMs with large memory (>64 GB) and high change rate, live migration can run forever. Plan offline migration in a maintenance window or upgrade the migration network.
See also
- One DC or two DCs for an SMB office?Two is almost always the right answer; one DC is a single point of failure for logon, DNS and GPOs.
- Should I split FSMO roles across two DCs?For a small domain all on one DC is fine; with two DCs splitting is tidier but not required.
- How do I know my AD replication is healthy?Replication errors creep in silently; they only surface when logins or GPOs misbehave.
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