Atomic Test And Set Of Disk Block Returned False For Equality ❲Original × 2027❳

[ Host / ESXi ] ---> Issues ATS (Compare & Write) ---> [ Storage Array ] | Verifies: Is Sector Data == Expected? / \ YES NO / \ [ Locks Block & Writes ] [ Fails: Returns False for Equality ] How ATS Works

In a highly dynamic cluster, multiple hosts frequently attempt to modify the same volume simultaneously (e.g., during mass virtual machine power-ons, migrations, or snapshot creations). If Host A and Host B both read a metadata block at the same time, Host A may successfully execute its ATS write first. When Host B attempts its ATS write milliseconds later, the metadata has changed. Host B’s "Test" phase fails because the disk block no longer matches its outdated cache. 2. Storage Path Flapping and Multipathing Misconfigurations

In vSphere, this can be done by changing the advanced setting: UserVars.VMFS3HardwareAcceleratedLocking to 0 (Disabled). [ Host / ESXi ] ---> Issues ATS

The most common scenario leading to this error is a . This occurs primarily during the heartbeat process, where an ESXi host periodically updates its "heartbeat" region on the VMFS volume to signal that it is still alive and maintaining its locks. When an ATS operation on a heartbeat slot fails with "false for equality," the ESXi host loses confidence in its lock on the datastore. This can trigger a series of events, including aborting all outstanding I/O to the datastore and resetting the SCSI device, leading to temporary connectivity loss and application disruptions.

The error message says: "returned false for equality." When Host B attempts its ATS write milliseconds

Verify VAAI integration compatibility and upgrade controller firmware.

Sometimes, adjusting how aggressively the ESXi host retries failed ATS operations can mitigate performance drops. You can modify the heartbeat timeout parameters via the vSphere CLI or Advanced Settings: If you share with third parties

When this error trips continuously, it ripples up the infrastructure stack:

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esxcli system settings advanced set -i 0 -o /VMFS3/UseATSForHBOnVMFS5

Examine your system logs (such as VMware vmkernel.log ) to map the error to a specific device identifier (NAA ID). Track down which physical hosts are actively reporting the error to see if the issue is isolated to a single blade chassis or widespread across the cluster. Step 2: Analyze Storage Latency Metrics