To understand this error, you must first understand hardware-level synchronization. What is Test-and-Set?
Therefore, the root cause is almost always in the or stale cache invalidation .
A critical failure in this mechanism is the error:
If the LUN is thin-provisioned, verify that there is sufficient free space on the array to accommodate its growth. The "could not find an empty HB slot" error is a strong indicator of this issue. If this is the case, the solution is to add more physical space to the thin-provisioned LUN.
Get-AdvancedSetting -Entity VMHost-Name -Name VMFS3.UseATSForHBOnVMFS5 | Set-AdvancedSetting -Value 0 -Confirm:$false
(vStorage APIs for Array Integration) is a set of storage primitives that offload certain storage operations from the ESXi host to the storage array. One of the most critical VAAI primitives is Atomic Test and Set (ATS) . On the wire, an ATS operation is implemented as a SCSI Compare and Write (CAW) command :
match, effectively denying the host access to that disk block. Resulting Symptoms Datastores becoming inaccessible or "grayed out" in vCenter.
If the Fibre Channel (FC), iSCSI, or NFS network experiences high latency or packet loss, the ATS command takes too long to reach the storage array. By the time the command arrives, the internal timer has expired, or another host has already completed a write operation, invalidating the original test state. Excessive Storage Contention (VDI and Boot Storms)
VMware provides a supported mechanism to revert the heartbeat locking to the legacy method (plain SCSI reads/writes). This does not disable ATS entirely but reverts the specific heartbeat component. This can be done without rebooting the host using the following command in the ESXi shell:
Implement randomized delays for boot schedules if using Virtual Desktop Infrastructure (VDI). Step 5: Evaluate ATS-Only Locking vs. ATS+SCSI
Ensure the Native Multipathing Plug-in (NMP) or third-party PowerPath software is configured according to vendor best practices.
“atomic test and set of disk block returned false for equality”
If nodes are failing to release locks before their leases expire, increase the lease duration. Ensure that your system has a reliable lock reclamation mechanism (e.g., a watchdog or a lock monitor).
Atomic Test And Set Of Disk Block Returned False For Equality
To understand this error, you must first understand hardware-level synchronization. What is Test-and-Set?
Therefore, the root cause is almost always in the or stale cache invalidation .
A critical failure in this mechanism is the error:
If the LUN is thin-provisioned, verify that there is sufficient free space on the array to accommodate its growth. The "could not find an empty HB slot" error is a strong indicator of this issue. If this is the case, the solution is to add more physical space to the thin-provisioned LUN.
Get-AdvancedSetting -Entity VMHost-Name -Name VMFS3.UseATSForHBOnVMFS5 | Set-AdvancedSetting -Value 0 -Confirm:$false
(vStorage APIs for Array Integration) is a set of storage primitives that offload certain storage operations from the ESXi host to the storage array. One of the most critical VAAI primitives is Atomic Test and Set (ATS) . On the wire, an ATS operation is implemented as a SCSI Compare and Write (CAW) command :
match, effectively denying the host access to that disk block. Resulting Symptoms Datastores becoming inaccessible or "grayed out" in vCenter.
If the Fibre Channel (FC), iSCSI, or NFS network experiences high latency or packet loss, the ATS command takes too long to reach the storage array. By the time the command arrives, the internal timer has expired, or another host has already completed a write operation, invalidating the original test state. Excessive Storage Contention (VDI and Boot Storms)
VMware provides a supported mechanism to revert the heartbeat locking to the legacy method (plain SCSI reads/writes). This does not disable ATS entirely but reverts the specific heartbeat component. This can be done without rebooting the host using the following command in the ESXi shell:
Implement randomized delays for boot schedules if using Virtual Desktop Infrastructure (VDI). Step 5: Evaluate ATS-Only Locking vs. ATS+SCSI
Ensure the Native Multipathing Plug-in (NMP) or third-party PowerPath software is configured according to vendor best practices.
“atomic test and set of disk block returned false for equality”
If nodes are failing to release locks before their leases expire, increase the lease duration. Ensure that your system has a reliable lock reclamation mechanism (e.g., a watchdog or a lock monitor).
