HCX Bulk Migration Retry Delays with Enable Seed Checkpoint Option
Article ID: 440767
Updated On:
Products
Issue/Introduction
When retrying a VMware HCX migration (Bulk or RAV) with the "Enable Seed Checkpoint" option selected, the synchronization process takes significantly longer than the original base synchronization.
Example Scenario:
- Initial Sync (150 GB VM): ~9 minutes.
- Retry with Seed Checkpoint: ~20–40 minutes.
- Observation: The retry consumes more time despite the expectation that reusing existing data would accelerate the process.
Environment
Product: VMware HCX 4.11.3
Cause
The delay is caused by the block checksum verification process.
This behavior is Operating as Designed. The "Seed Checkpoint" feature is primarily a bandwidth optimization mechanism, not a time-optimization tool.
When a migration retry utilizes existing seed data, HCX performs a mandatory block-by-block checksum verification to validate the integrity and consistency of the data already present on the target storage. The duration of this process is influenced by:
- Storage I/O Performance: The speed at which the hosts can read and verify local disk blocks.
- Host Resource Availability: CPU and RAM overhead required for checksum calculations.
Resolution
There is no misconfiguration or product defect. To optimize migration timelines, follow these strategic recommendations:
Use the "Enable Seed Checkpoint" feature in the following scenarios:
- Limited Bandwidth: When network throughput is a significant constraint and re-transmitting data is the primary bottleneck.
- Massive Workloads: For very large virtual machines where a network interruption would otherwise force a multi-day transfer to restart from zero.
- Resiliency: When the priority is bandwidth conservation and resilience against network instability rather than absolute completion speed.
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