Frequent in vSphere 5.5 Update 2 and later, where ATS is used by default for heartbeat liveness.
In the world of low-level storage engineering, few log messages inspire as much dread as the one that reads: . Frequent in vSphere 5
if (!success) log("Atomic test-and-set of disk block %d returned false for equality", block_number); // Expected content changed. Possibly: // - Another node updated it // - Our cached copy is stale // - Hardware mis-compare handle_concurrent_modification(); Possibly: // - Another node updated it //
Atomic test and set (often abbreviated as ATS) is a low-level disk operation that is used to test and set a flag on a disk block. The operation is atomic, meaning that it is executed as a single, indivisible unit, ensuring that either the test or the set operation completes successfully, but not both. To prevent data corruption, hosts use a locking mechanism
In a shared storage environment, multiple ESXi hosts often access the same Virtual Machine File System (VMFS) datastore. To prevent data corruption, hosts use a locking mechanism.