In VMware vSphere environments, reliable communication between compute, networking, and storage components is essential for maintaining virtual machine availability, performing seamless vMotion migrations, and ensuring consistent network configurations across ESXi hosts.
When one of these infrastructure components experiences performance degradation or connectivity issues, the resulting errors may appear to originate from an entirely different layer of the environment.
A common example is excessive storage latency or storage connectivity failures affecting ESXi management services. Under certain conditions, these issues can cause the hostd and vpxa services to become unresponsive, preventing the ESXi host from synchronizing its vSphere Distributed Switch (vDS) configuration with vCenter Server.
As a result, vMotion operations may fail, Distributed Port Group changes may not complete, and affected ESXi hosts may report an Out of Sync status.
This article explains the symptoms, underlying causes, log analysis techniques, and recommended troubleshooting procedures for identifying and resolving these issues in VMware ESXi 8.0 environments.
Understanding the Symptoms
The issue typically becomes noticeable when administrators attempt to perform network configuration changes or migrate virtual machines through the vSphere Client.
Affected ESXi hosts may exhibit one or more of the following symptoms:
- vMotion migrations fail when moving virtual machines from an affected ESXi host.
- Creating or modifying Distributed Port Groups fails.
- The vSphere Distributed Switch reports an Out of Sync status.
- The ESXi host becomes intermittently disconnected or unresponsive in vCenter Server.
- The
hostdandvpxamanagement services are stopped, unresponsive, or unable to process management requests.
During these operations, the vSphere Client may display an error similar to the following:
A general system error occurred: DVS error:
see fault Cause
Cannot create Distributed Port Group
dvportgroup-#### of VDS [VDS-NAME]
on the host [HOST-NAME]
Cause:
Cannot complete a vSphere Distributed
Switch operation for one or more
host members.This error indicates that vCenter Server was unable to complete a Distributed Switch operation on one or more participating ESXi hosts.
However, an important distinction must be made:
A DVS error does not necessarily indicate a problem with the physical or virtual networking infrastructure.
In certain situations, the underlying cause may be storage latency or connectivity issues that prevent ESXi management services from completing their operations.
Root Cause: Storage Latency and ESXi Management Service Failures
VMware ESXi relies on several background services to manage virtual machines, network configurations, storage resources, and communication with vCenter Server.
Two services are particularly important in this scenario.
hostd – ESXi Host Management Service
The hostd service is responsible for local ESXi management operations, including:
- Processing host configuration requests.
- Managing virtual machine operations.
- Handling local management API requests.
- Applying host-level configuration changes.
vpxa – vCenter Server Agent
The vpxa service provides the management communication interface between an ESXi host and vCenter Server.
Its primary responsibilities include:
- Receiving management instructions from vCenter Server.
- Coordinating host operations.
- Reporting host information and operational status.
- Supporting centralized administration of the ESXi host.
Under normal conditions, these services work together to maintain consistent configurations between vCenter Server and its managed ESXi hosts.
How Storage Latency Affects vDS Synchronization
When the storage infrastructure experiences severe I/O latency or connectivity failures, management operations that depend on datastore access may become delayed or blocked.
For example, if storage response times increase to several hundred milliseconds, operations requiring disk access may take significantly longer than expected.
In the affected scenario, Distributed Switch metadata operations involving the .dvsData directory on the datastore may be delayed or fail.
If hostd is unable to complete these operations, the service may become unresponsive, preventing vCenter Server from successfully applying network configuration changes.
This can result in an inconsistent vDS configuration between the ESXi host and vCenter Server.
The failure sequence can be summarized as follows:
Storage Latency or Storage I/O Failure → Delayed or Unresponsive hostd Operations → vCenter Management Communication Issues → vDS Synchronization Failure → vMotion or Port Group Operation Failure
This dependency explains why a networking-related error may originate from the storage subsystem rather than the network infrastructure itself.
Analyzing ESXi VMkernel Logs
The first troubleshooting step is to examine the ESXi VMkernel logs.
VMkernel logs contain valuable diagnostic information related to storage devices, hardware interactions, device drivers, and low-level I/O operations.
Connect to the affected ESXi host using SSH and examine the following log file:
/var/run/log/vmkernel.logTo identify storage-related errors, run:
grep -i "ScsiDeviceIO" /var/run/log/vmkernel.logExample: Storage I/O Failure
The following messages are based on the provided ESXi VMkernel log:
ScsiDeviceIO: 4697:
Cmd(0x...) 0x28 ... failed
H:0x0 D:0x2 P:0x0
Valid sense data: 0x4 0x84 0x0
These entries indicate that a SCSI command issued to a storage device failed.
The following table explains the most relevant fields:
| Parameter | Description |
|---|---|
ScsiDeviceIO | Indicates a SCSI I/O operation involving a storage device. |
Cmd 0x28 | Represents the SCSI READ(10) command. |
H:0x0 | Indicates no host-level error was reported. |
D:0x2 | Indicates a SCSI Check Condition status. |
P:0x0 | Indicates no plugin-level error was reported. |
Sense 0x4 | Represents a SCSI Hardware Error sense key. |
0x84 0x0 | Additional sense information that should be interpreted using device and vendor documentation. |
Interpreting the Error
Two fields are particularly important:
D:0x2indicates that the storage device returned a Check Condition status.Sense 0x4indicates that the device reported a hardware-related error condition.
These values suggest that the storage device was unable to successfully complete the requested read operation.
However, these messages alone do not conclusively prove that excessive storage latency is the root cause.
Additional investigation is required to determine whether the failure originates from:
- A physical disk or storage device.
- A storage controller.
- A SAN fabric or connectivity problem.
- An HBA or storage path issue.
- Another component within the storage infrastructure.
The naa.* identifier recorded in the log can help administrators identify the affected storage device and correlate the errors with the storage array.
Checking Storage Infrastructure Health and Performance
Before restarting management services or modifying network configurations, administrators should verify that the underlying storage infrastructure is operating correctly.
Storage-related issues should be investigated first because unresolved storage failures may cause management services to become unresponsive again.
Step 1: Identify Storage Devices
List the storage devices recognized by ESXi:
esxcli storage core device listReview the device information and identify the storage device associated with the naa.* identifier found in the VMkernel logs.
Step 2: Verify Storage Paths
Display the available storage paths:
esxcli storage core path listExamine the path states and look for unavailable, failed, or otherwise unexpected paths.
For SAN-based environments, verify connectivity between ESXi hosts, storage switches, and storage arrays.
Step 3: Analyze Storage Latency with esxtop
ESXi includes the esxtop utility for monitoring real-time system performance.
Start the utility:
esxtopPress u to display the disk device statistics.
Pay particular attention to the following metrics:
| Metric | Description |
|---|---|
DAVG/cmd | Average device-level I/O latency. |
KAVG/cmd | Average latency introduced at the VMkernel level. |
GAVG/cmd | Average total I/O latency observed by ESXi. |
Sustained high latency or unexpected increases in these values may indicate a storage performance problem.
Latency measurements should always be evaluated in the context of the storage technology, workload characteristics, and expected performance baseline.
Step 4: Investigate the Storage Backend
If shared storage or SAN infrastructure is used, review the following components:
- Storage disks and RAID groups.
- Storage controllers and controller failover status.
- Fibre Channel or iSCSI connectivity.
- SAN switches and backend fabric.
- HBA adapters and associated drivers or firmware.
- Storage array performance and diagnostic logs.
Where necessary, involve the storage vendor to investigate hardware faults, controller issues, or backend performance bottlenecks.
Restarting ESXi management services without resolving the underlying storage problem may provide only temporary relief.
Verifying and Restarting hostd and vpxa Services
After confirming that storage connectivity and performance have returned to a stable state, the next step is to examine the ESXi management services.
Step 1: Check Service Status
Connect to the ESXi host through SSH.
Check the status of the hostd service:
/etc/init.d/hostd statusCheck the status of the vpxa service:
/etc/init.d/vpxa statusIf either service is stopped or unresponsive, a controlled restart may be necessary.
Step 2: Restart the Management Services
Restart hostd:
/etc/init.d/hostd restartRestart vpxa:
/etc/init.d/vpxa restartThese commands restart the individual management services without intentionally restarting every ESXi service.
After completing the restart, allow sufficient time for the services to initialize and reconnect to vCenter Server.
Step 3: Review Management Service Logs
If the problem persists, inspect the following log files:
/var/run/log/hostd.log/var/run/log/vpxa.logLook for service initialization failures, datastore access errors, communication timeouts, or configuration synchronization problems.
Important Considerations for Production Environments
Some troubleshooting procedures recommend restarting all ESXi management services using:
services.sh restartHowever, this command should not be used indiscriminately.
In environments using technologies such as vSAN, NSX, LACP, or shared graphics configurations, restarting all services may introduce additional operational risks.
Where possible, restart only the affected services after reviewing the environment configuration and the potential impact.
Management service restarts may also interrupt active management tasks even when running virtual machines remain powered on.
Verifying vSphere Distributed Switch Synchronization
Once the storage infrastructure and management services are operating correctly, verify whether the affected ESXi host has successfully synchronized its Distributed Switch configuration with vCenter Server.
Open the vSphere Client and navigate to the Networking view.
Select the relevant vSphere Distributed Switch and review the synchronization status of its connected ESXi hosts.
A status of In Sync indicates that the host’s distributed networking configuration is synchronized with vCenter Server.
If the host continues to report Out of Sync, additional corrective actions may be required.
Before making any changes, determine which critical network services depend on the affected vDS.
These may include:
- ESXi Management Network.
- vMotion Network.
- vSAN Network.
- Virtual machine production networks.
- Other VMkernel or infrastructure connectivity.
Removing an ESXi host from a Distributed Switch without properly migrating its networking dependencies can cause management disconnection and virtual machine network outages.
For this reason, vDS removal and reattachment should be considered only after safer recovery methods have been evaluated.
Rebuilding vDS Host Membership to Restore Synchronization
If storage issues have been resolved, management services are healthy, and synchronization problems persist, rebuilding the affected host’s vDS membership may be considered.
This procedure allows the host to receive a fresh Distributed Switch configuration from vCenter Server.
Because the operation changes host networking, it must be carefully planned and preferably performed during an approved maintenance window.
Step 1: Document and Back Up the Network Configuration
Before modifying the Distributed Switch, record the existing configuration.
Review:
- Distributed Port Groups.
- VLAN assignments.
- MTU settings.
- Physical uplink mappings.
- VMkernel adapter assignments.
- Virtual machine network connections.
Where possible, export a backup of the vDS configuration.
Step 2: Secure Management Network Connectivity
If the ESXi Management Network currently uses the affected Distributed Switch, removing the host from the vDS may disconnect it from vCenter Server.
Before proceeding, migrate the necessary VMkernel adapters, physical uplinks, and virtual machine network connections to a suitable vSphere Standard Switch (vSS) or another supported network configuration.
Ensure that out-of-band management access, such as HPE iLO or Dell iDRAC, is available.
This provides an alternative recovery method if management connectivity is interrupted.
Step 3: Place the ESXi Host into Maintenance Mode
Before changing the host’s network membership, migrate running virtual machines to other ESXi hosts or shut them down safely according to the maintenance plan.
Then place the affected host into Maintenance Mode.
If vMotion is unavailable, an alternative workload evacuation procedure may be necessary.
Step 4: Remove the Host from the Distributed Switch
In the vSphere Client, navigate to:
Networking → vDS → Add and Manage Hosts → Remove hosts
Select the affected ESXi host and complete the removal process.
This action should only be performed after confirming that all critical networking dependencies have been safely migrated.
Step 5: Add the Host Back to the Distributed Switch
After removing the host, reopen the same management wizard:
Networking → vDS → Add and Manage Hosts → Add hosts
Select the affected ESXi host.
Reconfigure the required physical network adapters, VMkernel connections, and virtual machine networking assignments.
Verify that the uplink and Port Group mappings match the intended infrastructure design.
Step 6: Confirm Successful Synchronization
Once the host has been reattached, verify that the vDS synchronization status changes to In Sync.
Before exiting Maintenance Mode, validate Management Network connectivity, vMotion communication, and any other required infrastructure networks.
Rebooting the ESXi Host if Management Services Remain Unresponsive
If restarting the management services does not restore normal operation, a controlled ESXi host reboot may be considered.
However, this should be treated as a recovery measure rather than a direct fix for the underlying storage issue.
Before rebooting the host:
- Verify the state of all running virtual machines.
- Migrate or safely shut down workloads where necessary.
- Confirm that storage connectivity is stable.
- Review the expected impact on production services.
- Ensure that a recovery and rollback plan is available.
Restarting the ESXi host may restore management service functionality, but it does not repair a faulty storage device, controller, or SAN connection.
Therefore, the storage-related root cause must still be investigated and addressed.
Post-Recovery Validation
After completing the corrective actions, administrators should perform a final infrastructure health assessment.
The disappearance of the original error message does not necessarily mean that the underlying issue has been permanently resolved.
The following checks are recommended:
- Confirm that the ESXi host is displayed as Connected in vCenter Server.
- Verify that the vDS synchronization status is In Sync.
- Confirm that both
hostdandvpxaservices are running. - Recheck storage device and path states.
- Review storage latency metrics using
esxtop. - Confirm that no new
ScsiDeviceIOfailures are being generated. - Perform a controlled test vMotion operation.
- Validate Distributed Port Group assignments and VMkernel network connectivity.
If all checks complete successfully and storage performance remains stable, the host can return to normal production operations.
vMotion failures and vSphere Distributed Switch errors in VMware vSphere environments are not always caused by network configuration problems.
Severe storage latency, failed SCSI operations, or datastore connectivity issues can affect ESXi management services and prevent successful synchronization between an ESXi host and vCenter Server.
As a result, administrators may encounter DVS errors even when the underlying problem originates from the storage subsystem.
Effective troubleshooting requires a systematic approach that considers the dependencies between storage performance, management services, and distributed networking.
The recommended approach is to identify and resolve the underlying storage problem first, restore ESXi management services second, and modify Distributed Switch configurations only when necessary.
By following this sequence, administrators can reduce unnecessary configuration changes, minimize operational risks, and improve the reliability of their VMware virtual infrastructure.
