"Atomic test and set of disk block returned false for equality" is a low-level status message typically found in VMware ESXi VMkernel logs It indicates a failure in the Atomic Test and Set (ATS) , which is part of the vStorage APIs for Array Integration (VAAI) Core Concept: What is ATS?
: In some cases, vendors (like NetApp or Pure Storage) recommend disabling ATS for heartbeating if the storage array does not support it correctly under specific conditions. "Atomic test and set of disk block returned
When the operation returns "false," it is not merely reporting that the block was locked. It is reporting a collision in the timeline of the machine. It signifies that in the microscopic gap between the intention to act and the execution of the act, the universe changed. Another process, perhaps running on a core a fraction of a millisecond faster, or a network packet arriving from a continent away, touched that block first. The "false" is the system acknowledging that the operator was too late. It is the digital equivalent of reaching out to shake a hand only to find the other person has already turned away. It is reporting a collision in the timeline of the machine