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

The "atomic test and set of disk block returned false for equality" error is a protective measure. While it causes disruptive downtime, it exists to prevent the "silent killer" of enterprise computing: By failing the operation when the state doesn't match, the system ensures that two hosts never write to the same block simultaneously, preserving the integrity of your databases and virtual machines.

The host may mark the storage as "All Paths Down" (APD) or "Permanent Device Loss" (PDL) to protect data integrity.

Ensure your HBA (Host Bus Adapter) drivers and the storage array firmware are on the vendor's "Compatibility Matrix." The "atomic test and set of disk block

To understand the error, we first have to understand the mechanism. is a hardware-offloaded locking mechanism (often part of the VAAI—vSphere Storage APIs for Array Integration—feature set in VMware environments).

Use command-line tools (like esxcli storage core device vaai status get ) to ensure the array is actually reporting ATS as "supported." Conclusion Ensure your HBA (Host Bus Adapter) drivers and

This happens in a single, uninterruptible operation. Decoding the Error: "Returned False for Equality"

The host sent a command saying: "I want to lock this block. I expect the current owner ID to be 'X'." The storage array looked at the block, saw that the ID was actually 'Y', and replied: "False. The data is not what you expected." Common Causes Decoding the Error: "Returned False for Equality" The

Why would the equality test fail? Usually, it's one of three scenarios: 1. "Split Brain" or Multi-Host Contention

The VMkernel logs will fill with ATS Miscompare or Status: Op: 0x89 messages. How to Troubleshoot and Fix