Virtual machine power-on encounters "Ioctl" error with "Some of the disks of the virtual machine failed to load" due to snapshot chain inconsistency

Products

• VMware vSphere ESXi

Issue/Introduction

• Virtual machine power on attempt from the vSphere client fails with error:

File system specific implementation of Ioctl[file] failed

Additionally a warning similar to below is encountered on the virtual machine Summary page:

Some of the disks of the virtual machine <vm_name> failed to load. The information present for them in the virtual machine configuration may be incomplete

• Inspection of the virtual machine's Edit Settings reveals that one or more hard disks, running on snapshot, incorrectly display a capacity of 0 as illustrated below:

• On the ESXi host log where the concerned virtual machine resides, entries similar to below are observed:

/var/run/log/hostd.log

YYYY-MM-DDThh:mm:ss Wa(1##) Hostd[2####]: [Originator@6876 sub=Vmsvc.vm:/vmfs/volumes/<datastore_name>/<vm_directory>/<vm_name>.vmx] Load failed: cannot open /vmfs/volumes/<datastore_name>/<vm_directory>/<vm_disk-00000#>.vmdk (18): The parent virtual disk has been modified since the child was created. The content ID of the parent virtual disk does not match the corresponding parent content ID in the child

• On the virtual machine log for affected virtual machine, errors similar to below are encountered:

/vmfs/volumes/<datastore_name>/<vm_directory>/vmware.log

YYYY-MM-DDThh:mm:ss In(05)+ vmx - Power on failure messages: File system specific implementation of Ioctl[file] failed
YYYY-MM-DDThh:mm:ss In(05)+ vmx - The parent virtual disk has been modified since the child was created. The content ID of the parent virtual disk does not match the corresponding parent content ID in the child
YYYY-MM-DDThh:mm:ss In(05)+ vmx - Cannot open the disk '/vmfs/volumes/<datastore_name>/<vm_directory>/<vm_disk-00000#>.vmdk' or one of the snapshot disks it depends on.
YYYY-MM-DDThh:mm:ss In(05)+ vmx - Module 'Disk' power on failed.
YYYY-MM-DDThh:mm:ss In(05)+ vmx - Failed to start the virtual machine.
YYYY-MM-DDThh:mm:ss In(05)+ vmx -
YYYY-MM-DDThh:mm:ss In(05) vmx - Vix: [mainDispatch.c:4211]: VMAutomation_ReportPowerOpFinished: statevar=0, newAppState=1870, success=1 additionalError=0
YYYY-MM-DDThh:mm:ss In(05) vmx - Transitioned vmx/execState/val to poweredOff
YYYY-MM-DDThh:mm:ss In(05) vmx - Vix: [mainDispatch.c:4211]: VMAutomation_ReportPowerOpFinished: statevar=0, newAppState=1870, success=0 additionalError=0
YYYY-MM-DDThh:mm:ss In(05) vmx - Vix: [mainDispatch.c:4251]: Error VIX_E_FAIL in VMAutomation_ReportPowerOpFinished(): Unknown error

Cause

The warning "Some of the disks of the virtual machine <vm_name> failed to load. The information present for them in the virtual machine configuration may be incomplete" is encountered when the ESXi host fails to load the disks for concerned virtual machine properly.

Virtual machine snapshots maintain disk hierarchy using a Content ID (CID) mechanism. In a healthy chain, every child disk descriptor file (e.g., vm-00000#.vmdk) contains a reference (parentCID) that must match the CID of its parent disk.

In this scenario, the ESXi and virtual machine logs indicate a Snapshot Chain Inconsistency. A CID mismatch exists between the child and parent disks on one or more currently mounted hard disks. This break in the chain prevents the ESXi host from correctly enumerating the disks, leading to the power-on failure.

Resolution

To power on the virtual machine, restore the snapshot chain consistency by rectifying the CID mismatch between parent and child disk(s) for all affected hard disks using either of the below methods:

• Manual method: "The parent virtual disk has been modified since the child was created" error
• Scripted method: Locate and remediate CID/parentCID mismatches in snapshot descriptor files using a scripted method.

After successfully powering on the virtual machine, create a new temporary snapshot followed by a Delete All operation. This will commit all the data to the base disk(s) and clean up the snapshot hierarchy.