Block Returned False For Equality High Quality: Atomic Test And Set Of Disk

In traditional storage, locking a file required "SCSI Reservations," which locked an entire LUN (Logical Unit Number). This was inefficient. ATS allows for . Instead of locking the whole "parking lot," the system only locks a "single parking space" (a specific disk block). The process works like this:

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. In traditional storage, locking a file required "SCSI

If the host cannot "set" the lock, it cannot write to the disk. Instead of locking the whole "parking lot," the

Use command-line tools (like esxcli storage core device vaai status get ) to ensure the array is actually reporting ATS as "supported." Conclusion If the host cannot "set" the lock, it

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).

In some specific storage environments (notably certain older NAS or SAN setups), the ATS heartbeating mechanism is too aggressive. VMware allows you to revert to traditional SCSI reservations for heartbeating while keeping ATS for other tasks, though this should only be done under the guidance of support.

Look for spikes in command latency. ATS is very sensitive to timing; if the storage is overloaded, ATS failures will increase.