ONTAP FLI ESXi host remediation

05/06/2026 Contributors

Before running the ONTAP FLI migration on an ESXi host, complete these pre-migration steps. There are separate steps for offline and online migrations.

Pre-Migration - Offline FLI

This group of steps are common for both Online and Offline FLI. Before unprovisioning the source LUN from the host, ensure that the following steps have been completed.

VMs/VMDK	RDM	WSFC	VMSC
Step 1: Shut down guest VMs gracefully.	Step 1: For VMs using RDMs, Identify the backend mapping with nmp device and remove RDM disks gracefully.	Step 1: If WFSC is present, shut down the cluster gracefully and follow Windows remediation steps to remove disks.	Step 1: If VM-HA or VMSC is configured, disable HA, release heartbeat disk(s) if present, and adjust cluster configuration as needed.
Step 2: Unmount datastores planned for migration; if shared, unmount from all hosts.	Step 2: Detach relevant NMP devices involved in the migration.	Step 2: Shut down guest VMs gracefully.	Step 2: Unmount datastores planned for migration; if shared, unmount from all hosts.
Step 3: Check VMFS locking mode (ATS-only vs ATS+SCSI). If ATS-only, change to SCSI (required only for Online FLI).		Step 3: Unmount datastores planned for migration; if shared, unmount from all hosts. a	Step 3: Detach relevant NMP devices involved in the migration.
Step 4: Detach relevant NMP devices involved in the migration.		Step 4: Detach relevant NMP devices involved in the migration.

VMs/VMDK

RDM

WSFC

VMSC

Step 1: Shut down guest VMs gracefully.

Step 1: For VMs using RDMs, Identify the backend mapping with nmp device and remove RDM disks gracefully.

Step 1: If WFSC is present, shut down the cluster gracefully and follow Windows remediation steps to remove disks.

Step 1: If VM-HA or VMSC is configured, disable HA, release heartbeat disk(s) if present, and adjust cluster configuration as needed.

Step 2: Unmount datastores planned for migration; if shared, unmount from all hosts.

Step 2: Detach relevant NMP devices involved in the migration.

Step 2: Shut down guest VMs gracefully.

Step 2: Unmount datastores planned for migration; if shared, unmount from all hosts.

Step 3: Check VMFS locking mode (ATS-only vs ATS+SCSI). If ATS-only, change to SCSI (required only for Online FLI).

Step 3: Unmount datastores planned for migration; if shared, unmount from all hosts. a

Step 3: Detach relevant NMP devices involved in the migration.

Step 4: Detach relevant NMP devices involved in the migration.

Key points to know

The ATS-only setting is stored in the VMFS header, which resides on the first extent of the datastore. If the datastore spans multiple extents, only the first extent needs remediation.
If the datastore is shared across multiple ESXi hosts, updating it from one host is typically sufficient; other hosts pick up the change after a rescan/remount.
No active I/O can be running against the datastore while changing ATS-only mode. VMware guidance is to evacuate/migrate or shut down VMs and unmount/remount as required to apply the change.

ESX Example Commands: Sync Block

Put Host in Maintenance Mode

esxcli system maintenanceMode set --enable true

Identify storage devices and datastores

esxcli storage core device list
esxcli storage filesystem list

Check VMFS ATS locking mode

vmkfstools --queryfs -h /vmfs/volumes/<DATASTORE_NAME>

Unmount the datastore (repeat on all ESXi hosts if shared)

esxcli storage filesystem unmount -l <DATASTORE_NAME>

Detach the backing device (NMP / naa device)

esxcli storage core device set -d <naa.ID> --state=off

Verify device is detached

esxcli storage core device list -d <naa.ID>

Rescan after detaching to confirm clean state

esxcli storage core adapter rescan --all

Exit maintenance mode after completion

esxcli system maintenanceMode set --enable false

Pre-Migration - Online FLI

Below are specific steps of online FLI but these steps must be preceded by steps in the Pre-Migration Offline FLI.

The following steps must be carried out after the NetApp LUN is provisioned to the Host.

At this point the lun import is already created, lun is mapped to the host igroup and there is either iSCSI or FC Initiator logged in from the Host.

In case of offline FLI the NetApp LUN remains in offline state.

VMs/VMDK	RDM	VMSC
Step 1: Rescan storage on all mapped ESXi hosts.	Step 1: Rescan storage on all mapped ESXi hosts.	Step 1: Rescan storage on all mapped ESXi hosts.
Step 2: List volume/device details to confirm filesystem details on the LUN.	Step 2: Identify new NAA IDs and add RDMs back to the respective VMs.	Step 2: List volume/device details to confirm filesystem details on the LUN.
Step 3: Identify datastore details and mount datastores back to ESXi.	Step 3: Power on guest VMs and start applications.	Step 3: Identify datastore details and mount datastores back to ESXi.
Step 4: Power on guest VMs and start applications.		Step 4: Power on guest VMs and start applications.
		Step 5: Power on guest VMs and start applications

VMs/VMDK

RDM

VMSC

Step 1: Rescan storage on all mapped ESXi hosts.

Step 2: List volume/device details to confirm filesystem details on the LUN.

Step 2: Identify new NAA IDs and add RDMs back to the respective VMs.

Step 2: List volume/device details to confirm filesystem details on the LUN.

Step 3: Identify datastore details and mount datastores back to ESXi.

Step 3: Power on guest VMs and start applications.

Step 3: Identify datastore details and mount datastores back to ESXi.

Step 4: Power on guest VMs and start applications.

Step 5: Power on guest VMs and start applications

Refer to OS Vendor Documentation for latest and updated command list.

Put Host in Maintenance Mode