Distinguishing vSAN Issues from Guest OS Boot Problems After DR Failover

Products

• VMware vSAN

Issue/Introduction

After a disaster recovery (DR) failover, virtual machines (VMs) may fail to boot properly. This article helps identify whether the issue is related to vSAN infrastructure or guest operating system (OS) boot problems.

Environment

- vSphere environment with vSAN
- Disaster Recovery setup (e.g., using replication technologies like Zerto)
- Windows guest operating systems

Cause

VM boot failures after DR failover can stem from various sources, including:
1. vSAN infrastructure issues
2. VM configuration problems
3. Guest OS boot manager corruption
4. Replication inconsistencies

Resolution

Follow these steps to troubleshoot and identify the root cause:

1. Check vSAN health:
   a. Log in to vCenter Server
   b. Navigate to the affected cluster
   c. Go to the "Monitor" tab and select "vSAN" > "Health"
   d. Verify that all health checks pass

2. Examine VM configuration:
   a. Right-click the affected VM and select "Edit Settings"
   b. Confirm that all virtual disks are present and properly configured
   c. Verify that the VM hardware version is compatible with the current environment

3. Inspect VM files:
   a. Browse the datastore containing the VM
   b. Confirm the presence of all necessary VM files (e.g., .vmx, .vmdk)
   c. Check file permissions and ensure they are correct

4. Review VM console output:
   a. Open the VM console
   b. Observe the boot process and note any error messages
   c. If the VM is stuck at a BIOS-like screen, this may indicate a guest OS issue

5. Verify vSAN object health:
   a. Use the vSphere Client to locate the VM's storage objects
   b. Check the health status of each object
   c. Ensure all components are accessible and in a "NORMAL" state

6. If steps 1-5 show no issues, suspect a guest OS problem:
   a. Consider engaging Microsoft support for Windows boot troubleshooting
   b. Explore guest OS repair options, such as using recovery tools or boot repair utilities

7. Check replication logs:
   a. Review logs from your replication software (e.g., Zerto)
   b. Look for any inconsistencies or errors during the failover process

8. Test with a new VM:
   a. Create a new VM with similar specifications
   b. Attempt to power it on in the DR environment
   c. If successful, this further indicates a guest OS issue with the original VM

Additional Information

vSAN Health Checks:
- Check vSAN Health
- About the vSAN Health Service
- Monitoring vSAN Health