Issue

Use this article to troubleshoot multiple ZSphere Windows VMs that recover after manual startup following black screens or freezes.

Symptoms

• Multiple Windows VMs display black screens and recover after manual startup.
• Management-node services, storage status, and the libvirtd service appear normal.

Environment

• Product: ZVF
• Version: 4.x
• Component: ZSphere
• Affected object: VM stability
• Scenario: VM runtime issues. Confirm the current version, deployment topology, storage type, and operation timeline.

Possible causes

• Insufficient guest OS resources, blue screens or black screens, drivers, or patches.
• CPU or memory pressure, storage I/O, or network jitter on physical hosts causes VMs to freeze.
• No obvious platform-service exception is recorded, requiring cross-verification from the VM and host sides.

Resolution

Perform the following checks in sequence, and record the affected objects, occurrence time, complete error messages, and current state.

1. Count affected VMs and hosts, record the occurrence time, and determine whether they are concentrated in the same resource pool.
2. Check host resources, storage I/O, libvirt/qemu logs, and VM events.
3. In Windows, check Event Viewer, blue-screen dumps, and driver logs.
4. Do not restart VMs in bulk immediately. Preserve one affected VM for evidence collection first.

Remediation

1. First determine whether affected VMs are concentrated on the same host, resource pool, or storage path to rule out a common infrastructure fault.
2. After preserving evidence from the affected VM, perform controlled recovery for one VM. Before bulk recovery, have ZStack technical support confirm the root cause and operational impact.

Verification

• Recovered VMs run stably, with no persistent freezes or blue-screen events in the guest OS.
• Host, storage, and management logs show no persistent exception in the same time window.