vSAN Health Service - Unexpected number of fault domains

Products

• VMware vSAN

Issue/Introduction

The Unexpected number of fault domains check in the vSAN Health Service verifies that exactly two fault domains are configured for data sites. If this health check is not green (OK), the vSAN (formerly known as Virtual SAN) stretched cluster has configuration problems that affect its operation.

Each data site must reside in a different fault domain. The total number of fault domains for data sites must be two.

The witness host cannot join the fault domain of either data site. Its fault domain name can be empty, which means the host itself is in a standalone fault domain. If you configure a name for the fault domain of the witness host, the name must be different from the fault domain of either data site.

Environment

VMware vSAN 6.1.x
VMware vSAN 6.2.x
VMware vSAN 6.0.x

Resolution

Follow these guidelines to prevent or resolve the error state:

• Verify that the stretched cluster has two data sites and one witness host.
• Configure the fault domains for the stretched cluster so that each data site resides in a separate fault domain.
• Place the witness host in a different fault domain than the data sites.

You can run the esxcli vsan faultdomain command to view and reconfigure the fault domain of each host.

Additional Information

For translated versions of this article, see:

• 日本語: 障害ドメイン数の確認 (2139367)
• 简体中文: vSAN 运行状况服务 - 容错域数量异常 (2144859)