"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?
The Goal:
Change the value of a disk block from "State A" to "State B." "Atomic test and set of disk block returned
"atomic test and set of disk block returned false for equality."
In the world of distributed systems, high-availability clusters, and storage area networks (SANs), data integrity is the highest priority. One of the most cryptic yet significant errors a systems administrator or storage engineer might encounter is: Conduct a thorough review of system logs to
Virtual Machines freezing:
If the host cannot "set" the lock, it cannot write to the disk. Definition of the Operation The "Equality" Failure The
Use sg_compare_and_write (from sg3_utils) to test the atomic operation:
- Conduct a thorough review of system logs to identify any related errors or warnings.
- Implement additional logging or tracing to monitor disk block access and modifications.
- Perform the test under controlled conditions to isolate the issue.
Definition of the Operation
The "Equality" Failure
The Check:
Before writing "State B," the system verifies that the block is still actually in "State A."
