Atomic Test And Set Of Disk Block Returned False For Equality __link__ Site
: Frequent LUN reset or ATS failure messages appearing in the vmkernel.log . Potential Resolutions
If they match (), the array updates the block with the new data.
This is a detailed technical guide regarding the error condition where an .
Cross-reference the naa.xxxxxxxxxxxxxxx string with your storage inventory to pinpoint exactly which datastore is experiencing the conflict. Step 2: Clear Stale Locks (The Temporary Fix) : Frequent LUN reset or ATS failure messages
Check if multiple hosts are logging the error for the exact same volume ID (UUID) simultaneously, which points to a contention or fabric issue. Step 2: Correlate with Infrastructure Events
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:
Note: Disabling ATS completely is highly discouraged in modern setups as it drastically reduces storage performance. Always consult your storage vendor's compatibility matrix before changing advanced advanced storage parameters. Conclusion Cross-reference the naa
If dozens of virtual machines on different hosts are booting, taking snapshots, or deleting files simultaneously, they all flood the storage array with ATS metadata updates. If Host A reads the block, and Host B modifies it before Host A can execute its "Set" command, Host A’s subsequent ATS command will fail for equality. 2. Storage Array Firmware Bugs
If the data does not match, the array returns an status, which the hypervisor surfaces as "Atomic test and set of disk block returned false for equality" . 2. Root Causes of the Error
: If you are seeing "Lost access to datastore" messages alongside this error, VMware often recommends disabling ATS for heartbeating (switching back to legacy SCSI reservations) as a workaround on affected arrays. This does not disable ATS entirely but reverts
The following steps will be taken to address this issue:
Did this happen during a like a backup, live migration, or storage path failover? Share public link
If (Current Disk State)==Expected State→Write New State (Returns True)If (Current Disk State) equals equals Expected State right arrow Write New State (Returns True)
