Atomic Test And Set Of Disk Block Returned False For Equality May 2026

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).

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

When the system reports that this operation "returned false for equality," it means the phase failed. To understand the error, we first have to

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:

The host checks the current metadata of a disk block to see if it matches what it expects. When the system reports that this operation "returned

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

Not all storage arrays implement VAAI/ATS the same way. If there is a bug in the array's microcode or if the host's driver is sending a malformed request, the array might reject the ATS heartbeat, leading to "false for equality" errors even if no real contention exists. 3. Network Latency and Heartbeating Issues Why would the equality test fail

Understanding the "Atomic Test-and-Set of Disk Block Returned False for Equality" Error