intended to acquire a lock or update a block, expecting value Voldcap V sub o l d end-sub Process A sent a command: "If block is Voldcap V sub o l d end-sub , change to Vnewcap V sub n e w end-sub Result: The operation returned false .
Operations like powering a VM on or off, creating a snapshot, vMotion migrations, or cloning vDisks hang indefinitely or fail outright.
This cryptic error message emerges from the heart of VMware's advanced storage integration, specifically pointing to a problem with a mechanism used to maintain data integrity. Understanding why a simple equality test fails requires exploring the layers of a modern virtualized data center, from the hypervisor's filesystem down to the storage array's firmware. intended to acquire a lock or update a
In the world of low-level systems programming and distributed databases, few error messages are as cryptic—and as critical—as If you have encountered this error while working with a clustered file system, a distributed lock manager, or a custom storage engine, you know the frustration it brings. The operation failed unexpectedly, leaving your application in an inconsistent state.
Look for spikes in command latency. ATS is very sensitive to timing; if the storage is overloaded, ATS failures will increase. Understanding why a simple equality test fails requires
Reorder writes so that the TAS block is the last write in a critical section. Use fdatasync() or O_SYNC to ensure the TAS write is persisted before proceeding. This prevents scenarios where a crash leaves the block in an unexpected state after recovery.
Here, you expected the block to contain 1 (meaning “free to write”), but it actually contained 5 . You need to decode what 5 means in your system: is it a node ID? A version number? A checksum? Look for spikes in command latency
dlm: atomic test and set of disk block 1048576 returned false for equality (expected=0, got=1002) dlm: lock acquisition failed. Node 1002 already owns the lock.
If a storage array is performing background operations—such as replication, automated tiering, deduplication, or taking hardware snapshots—it may manipulate block allocations without notifying the hypervisor immediately. Similarly, if another host in the cluster loses network connectivity but remains active (a split-brain scenario), both hosts might attempt to claim the same metadata heartbeats simultaneously. 3. Symptoms and Operational Impact
