Storage Migration Guidelines: Moving Standalone and Clustered VMs from vSAN Datastore to iSCSI and FC Storage

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Storage Migration Guidelines: Moving Standalone and Clustered VMs from vSAN Datastore to iSCSI and FC Storage

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Article ID: 449163

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Updated On:

Products

VMware vCenter Server

Issue/Introduction

Purpose:

To outline the expected impact and step-by-step procedures for migrating virtual machines from a vSAN datastore to an iSCSI SAN. This covers standard standalone VMs (e.g., VDI Management VM) and clustered VMs utilizing shared virtual disks (VMDKs).

Environment

VMware vSAN 7.x
VMware vSAN 8.x

Resolution

Scenario A: Standalone VM Migration

Expected Impact: Zero Downtime Standard virtual machines support online Storage vMotion. The VM can be migrated while fully powered on and actively serving users.

Migration Procedure:

Log in to the vSphere Client and locate the VM in the inventory.
Right-click the virtual machine and select Migrate.
Select Change storage only as the migration type and click Next.
Select the target iSCSI SAN datastore. Ensure the Compatibility checks succeeded message appears at the bottom of the window.
Choose the appropriate virtual disk format (e.g., Same format as source or Thin Provision) and assign the correct VM Storage Policy for the iSCSI array.
Review the settings and click Finish. Monitor the migration progress in the Recent Tasks pane.

Scenario B: Clustered VMs with Shared Disks

Expected Impact: Downtime Required

Virtual machines utilizing shared disks (multi-writer flag or physical SCSI bus-sharing for Microsoft WSFC, Oracle RAC, etc.) do not support live Storage vMotion. A cold migration is mandatory. You must manually manage the shared disk attachments to prevent data corruption or split-brain scenarios.

Migration Procedure:

1.Document Current SCSI Configurations:

Crucial for successful reattachment.
Edit the settings of the primary VM and document the SCSI controller settings, SCSI controller number, and SCSI ID for every shared disk. Note the exact datastore paths.

2.Gracefully Shut Down Cluster Services:

Log into the guest operating systems and stop the clustering application (e.g., SQL Server, Oracle) according to vendor best practices to ensure all pending data is flushed to disk.

3.Power Off Virtual Machines:

Secondary nodes first, then primary
Shut down the guest OS on all secondary/passive nodes in the cluster. Once the secondary nodes are fully powered off, shut down the primary/active node.

4.Detach Disks from Secondary Nodes:

Choose 'Remove from VM only' — do NOT delete files.
Right-click the secondary VMs, select Edit Settings, and remove all shared virtual disks. Selecting "Delete from datastore" will permanently destroy your cluster data.

5.Perform Cold Migration:

Right-click each VM in the cluster (primary and all secondary nodes) and perform a Storage vMotion to the new target iSCSI SAN datastore.

6.Reattach Shared Disks to Secondary Nodes:

Right-click the secondary VMs and select Edit Settings. Add an existing hard disk, browse to the new iSCSI datastore, and attach the shared disks. They must be mapped to the exact same SCSI IDs documented in Step 1.

7.Power On the Cluster:

Primary node first, then secondary.
Power on the Primary/Active VM first. Wait for the operating system to boot and the cluster services to fully initialize. Once verified, power on the secondary/passive nodes.