HCX UI reports an alert related to the "High data churn" during RAV delta synchronization.

Products

• VMware HCX

Issue/Introduction

• An alert indicating that a virtual machine with “High data churn” was detected during RAV delta synchronization is reported on the HCX UI.
  

  Message: High data churn detected for the Virtual Machine corresponding to the migration '<UUID>'

  
  
  
• A log indicating that an "Received RPO violation event" is logged to app.log.
  /common/logs/admin/app.log
  

  <timestamp> UTC [ReplicationTransferService_SvcThread-1098, Ent: DEFAULT, , TxId: <id>] INFO  c.v.h.s.r.j.ContinuousReplicationJob- Received RPO violation event for the transfer '<UUID>': {"rpoViolation":true,"rpoViolationInMinutes":1}

  
  
  
• The churn data transfer rate did not exceed the available bandwidth.
  /common/logs/admin/app.log
  

  <timestamp> UTC [ReplicationTransferService_SvcThread-1124, Ent: HybridityAdmin, , TxId: <id>] INFO  c.v.h.s.r.utils.ReplicationUtil- The Virtual Machine '<VM>' corresponding to the transfer '<UUID>' is churning data at the rate of 99 KBps which is within available bandwidth 25000 KBps

Environment

VMware HCX

Cause

Churn represents the frequency at which data or workloads are created, deleted, or modified.
HCX measures activities that may fail during migration and reports alerts when necessary.
When data synchronization occurs using vSphere Replication, a decrease in network or storage speed during delta synchronization may prevent the processing of data volumes within the specified timeline.
In such cases, it is determined that the required SLA is not met, triggering an RPO violation.

For RPO violations, please refer to the following document.
vSphere Replication RPO Violations

Resolution

You must verify that the network quality and storage performance within or between sites meet the system requirements.
For system requirements, please refer to the following document.
System Requirements
Requirements for Replication Assisted vMotion
Minimum Network Underlay Requirements for HCX