Unsupported ESX Version error after upgrading ESXi hosts to vSphere 9 without meeting VAIO requirements

Unsupported ESX Version error after upgrading ESXi hosts to vSphere 9 without meeting VAIO requirements

Machine-distilled from a resolved support ticket on 2026-09-28. Source ref: c9e9f6b83888. Verify before relying on it.

Applies to: Zerto 10.8 (including Update 1) on vSphere, where ESXi hosts are upgraded to version 9.x

Symptom: After ESXi hosts in a Zerto protected environment are upgraded to version 9.0.x, Zerto reports an 'Unsupported ESX Version' error for those hosts.

Cause: Zerto support on ESXi 9 depends on VAIO (vSphere APIs for IO Filtering) based protection. The agent's guidance indicates the likely cause was that VAIO had not been deployed at the version required by the Zerto Interoperability Matrix, so Zerto treated the upgraded hosts as unsupported. The customer did not confirm the VAIO state before rolling back, so this cause was not verified.

Resolution: 1. Before upgrading any ESXi host to version 9, check the Zerto Interoperability Matrix for the ESXi and VAIO versions supported by your Zerto release.

2. Deploy and configure VAIO with Zerto as described in the Zerto documentation, and confirm that all VAIO prerequisites and caveats can be met in the environment.

3. If hosts have already been upgraded and the VAIO requirements cannot be met straight away, roll the hosts back to ESXi 8 to restore supported operation.

4. Plan the ESXi 9 upgrade again only once the VAIO requirements are fully in place.

Sources:

• https://help.zerto.com/bundle/Linux.ZVM.HTML.10.8/page/VAIO_with_Zerto.htm