Atomic Test And Set Of Disk Block Returned False For Equality !!top!! Guide

In traditional storage systems, a host would lock an entire storage volume (LUN) using SCSI reservations to make a metadata change. This process was inefficient and slowed down performance.

: The host may issue a full reset on the LUN to "clear the air," which aborts all active I/O for every VM on that datastore. Degraded Path Redundancy

The error message "atomic test and set of disk block returned false for equality" is a critical VMware ESXi kernel error related to VAAI (vSphere Storage APIs Array Integration)

: If the error persists, the storage array may be misreporting its state or requiring a specific ATS configuration. Engage Broadcom Support : For severe cases involving In traditional storage systems, a host would lock

Which (e.g., ESXi 7.0, ESXi 8.0) is throwing this error?

The observation that an atomic test and set operation on a disk block returned false for equality highlights a potential issue with data consistency or concurrent access. Further investigation and debugging are necessary to resolve the root cause and ensure the reliability of disk operations.

This error commonly causes cluster-wide degradation, failing virtual machine operations (such as powering on/off, provisioning, or vMotion), and localized storage lockouts. Understanding why this happens requires looking at how modern hypervisors interact with Storage Area Networks (SANs). 1. The Core Architecture: Understanding VAAI and ATS Degraded Path Redundancy The error message "atomic test

The storage array looks at the actual block on the disk. If the current disk data matches the "expected" data provided by the host, the array permits the write operation.

In a shared storage environment, multiple server nodes (ESXi hosts) read and write to the same logical unit number (LUN) or datastore. To prevent data corruption, a host must secure a lock before modifying metadata (e.g., creating a file, extending a virtual disk, or updating a heartbeat).

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 Further investigation and debugging are necessary to resolve

Did this happen during a like a backup, live migration, or storage path failover? Share public link

If a system is logging "Atomic Test and Set returned false" unexpectedly or excessively, the following issues should be investigated:

If the instruction returns false, the equality has been rejected. The expected reality and the actual reality are out of sync. This is a fundamental rupture in the cognitive model of the software. The program operates under a linear assumption: "I checked the block; it appeared free; therefore, I will take it." The atomic test-and-set is the harsh correction to this assumption. It forces the software to confront the truth that looking is not touching, and seeing is not holding.