Atomic Test And Set Of Disk Block Returned False For Equality ^new^ 💯

: It issues a command to the storage array to update the block only if the current value still matches the "compare" value.

This report will be updated as more information becomes available. If you have any questions or concerns, please do not hesitate to reach out.

ret = atomic_compare_and_swap(block, expected, new);

In the world of computing, concurrency control is a fundamental challenge. When multiple processes or servers need to access the same shared resource—like a file or a disk block—they must have a way to coordinate and avoid conflicts. This is where the concept of the "atomic test and set" (ATS) operation comes into play. It’s a powerful, low-level instruction that allows a system to check the state of a variable (the "test") and, if it meets a certain condition, update it (the "set") in a single, uninterruptible step. This ensures that only one process at a time can claim ownership of a resource. : It issues a command to the storage

sg_persist -k /dev/sdX # Show registered reservation keys sg_persist -r /dev/sdX # Show reservation details

# Register a new key sg_persist -o -G -K 0x12345678 /dev/sdX

Note: This should be used as a temporary troubleshooting step, as disabling ATS can reduce overall metadata performance on highly consolidated clusters. Upgrade Storage Controller Firmware It’s a powerful, low-level instruction that allows a

Imagine a cluster with two nodes both trying to claim ownership of a shared LUN (Logical Unit Number). Each node issues:

Caution: Only clear reservations if you are certain no active node holds them.

The "Atomic test and set of disk block returned false for equality" error in VMware vSphere indicates a failure in Hardware Assisted Locking (ATS) due to outdated storage metadata, usually caused by concurrency conflicts or high latency. This failure occurs when an ESXi host attempts to update a storage block that has already been modified by another host, requiring investigation into firmware compatibility or disabling ATS heartbeats. For a detailed technical breakdown of this specific issue, review the discussion at Reddit . Step-by-Step Troubleshooting and Resolution

If the values match ( True for equality), the host atomically writes its new metadata or lock status to that block.

ATS requires rapid communication between the host and the storage array. High latency, dropped packets, or fabric errors on Fibre Channel (FC) or iSCSI networks can delay the ATS payload. If the command times out or arrives late, the block state may have altered in the interim. 4. Mixed Locking Mechanisms (ATS vs. SCSI-3 Reservations)

Host log files (such as /var/log/vmkernel.log ) become flooded with SCSI status errors ( H:0x0 D:0x2 P:0x0 Valid sense data: 0xe 0x1d 0x0 ), degrading management plane performance. Step-by-Step Troubleshooting and Resolution