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

The host checks the current metadata of a disk block to see if it matches what it expects.

Use command-line tools (like esxcli storage core device vaai status get ) to ensure the array is actually reporting ATS as "supported." Conclusion The host checks the current metadata of a

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 The data is not what you expected

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

In clustered environments (like VMware VMFS datastores), hosts use ATS as a "heartbeat" to tell other hosts they are still alive. If the network between the host and the storage has high latency or dropped packets, the update might arrive late or out of sync, causing the "equality" check to fail because the host is working with stale metadata. Impact on Operations When this error occurs, you will typically notice:

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