Atomic Test And Set Of Disk Block Returned False For Equality !!better!! Jun 2026

Verify that your entire data path is aligned with your hardware vendor's Matrix.

Resolving persistent ATS equality failures requires a systematic investigation across your virtualization and storage layers. Step 1: Analyze VMkernel Logs

The primary source of information is the vmkernel.log file on the ESXi host. Look for messages containing ATS Miscompare , Cmd 0x89 , or the exact error phrase. Pay attention to the timing and the specific device ( naa.xxx ) involved. Verify that your entire data path is aligned

If the storage array continues to fail handling ATS commands under load, you can temporarily revert to traditional SCSI reservations for datastore heartbeats. This forces the system to use standard locking mechanisms instead of VAAI ATS for basic up-time checks.

esxcli system settings advanced list -o /VMFS3/HardwareAcceleratedLocking Use code with caution. Look for messages containing ATS Miscompare , Cmd

: The host reads a specific disk block (metadata) and notes its current state.

: It often occurs in clustered environments where multiple hosts share the same datastore. A "false for equality" result means the host could not acquire a lock on the metadata because another entity had already updated or locked it. This forces the system to use standard locking

If a node crashes unexpectedly, it may leave a stale lock on a specific disk block. When a surviving node attempts to acquire or modify that block using an ATS instruction, the existing lock metadata causes the equality check to fail. How to Diagnose and Troubleshoot

The message is a critical diagnostic error typically associated with VMware ESXi and storage systems using VAAI (vSphere Storage APIs – Array Integration) .