Atomic Test And Set Of Disk Block Returned False For Equality

A return value of false indicates that the atomic condition was not met.

Symptom: A 4-node GlusterFS cluster began throwing “atomic test and set of disk block returned false for equality” errors after a power outage. Metadata operations hung, and thick provisioning failed.

Root cause: The power outage caused two nodes to believe they owned the same disk block region (split-brain). The DLM’s internal block version counter had reverted to 0 on one node after unclean shutdown. A return value of false indicates that the

Fix:

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). Root cause: The power outage caused two nodes

A return of false is a safe failure. It guarantees that the caller did not proceed under the assumption that they had exclusive access. This preserves data integrity. If the operation had erroneously returned true while another process held the lock, a race condition would occur, leading to data corruption on the disk block.

In the world of low-level storage systems, distributed databases, and concurrent programming, few errors are as cryptic—yet as critical—as the message: "atomic test and set of disk block returned false for equality." Ensure that your system has a reliable lock

If you have encountered this error, you are likely dealing with a race condition, a failing distributed lock, or a corrupted storage volume. This article dissects the error message piece by piece, explains the underlying mechanics of atomic operations on disk blocks, and provides a comprehensive guide to diagnosing and fixing the issue.