vSAN storage capacity expansion best practices using Ensure Accessibility

Products

• VMware vSphere ESXi

Issue/Introduction

When expanding vSAN capacity by adding physical disks to existing disk groups, you must decide whether to perform the expansion while virtual machines (VMs) are running or place the hosts into Maintenance Mode. This article provides the recommended procedural steps to ensure data availability and minimize performance impact during capacity expansion in a production environment.

Symptoms

• New physical drives are installed but not yet claimed by vSAN.
• Need to increase the overall vSAN datastore capacity in a cluster.
• Requirement to confirm if Maintenance Mode is mandatory for adding disks to a disk group.

Environment

• VMware vSAN 8.x

Cause

While vSAN supports the "hot" addition of capacity disks to an existing disk group, performing this operation on active nodes carrying production workloads can cause I/O contention during the subsequent resynchronization and rebalancing tasks.

Resolution

To minimize risk and ensure accessibility, follow these steps sequentially for each host in the cluster:

1. Verify that the newly added physical drives appear as Unclaimed in the vSphere Client under the host's storage devices.
2. Select the first host and place it into Maintenance Mode.
3. When prompted for vSAN data evacuation, select the Ensure Accessibility option. This guarantees that at least one replica of all VM data remains available in the cluster.
4. Navigate to the vSAN Disk Management view and Claim the new physical disks into the existing disk group.
5. Exit Maintenance Mode for the host.
6. Monitor the vSAN Resyncing Objects view. Wait for all resynchronization tasks to complete and for the cluster to return to a healthy state before proceeding to the next host.
7. Repeat steps 2 through 6 for each remaining host in the cluster.
8. • For more information on data evacuation options, see vSAN Data Resync After Exiting Ensure Accessibility Maintenance Mode.
     
     
   • To speak with a customer representative or a Support Engineer,  Contact Broadcom support . Scroll to the bottom of the page and click on your respective region.

Additional Information

• • For more information on data evacuation options, see vSAN Data Resync After Exiting Ensure Accessibility Maintenance Mode.
    
    
  • To speak with a customer representative or a Support Engineer,  Contact Broadcom support. Scroll to the bottom of the page and click on your respective region.