Microsoft Fabric Error:
AzureStorageOperationFailedConcurrentWrite
What does this error mean?
Multiple concurrent Fabric Data Factory copy activities are writing to the same Blob Storage or ADLS Gen2 file simultaneously, causing a write conflict. Azure Blob Storage does not support concurrent writers to the same file path.
Common causes
- 1Multiple copy pipeline runs are active simultaneously and all target the same output file path
- 2A pipeline with parallelism enabled has multiple partitions all writing to the same sink file
- 3An external process (another pipeline, application, or script) is also writing to the same blob path while the copy activity runs
How to fix it
- 1Identify which pipelines write to the same output path — in Fabric Monitor, filter runs by time and check whether multiple copy activities target the same file or folder path simultaneously.
- 2Redesign concurrent pipelines to write to separate output paths or partitions, then merge results in a subsequent step after all writes complete.
- 3Add pipeline dependencies (activity success conditions) to serialize writes that must target the same path — do not rely on scheduling offsets to prevent conflicts.
- 4If using ADLS Gen2 (hierarchical namespace), enable directory-level atomic operations and use the rename-on-write pattern: write to a temp path, then atomically rename to the target path.
- 5For high-throughput scenarios, partition the write target by date, region, or batch ID so concurrent writers each own a non-overlapping set of paths.
Beyond the docs
Common practitioner solutions not covered in the official documentation.
- 1Ensure only one pipeline run writes to a given file path at a time — add a pipeline trigger filter or sequential execution constraint
- 2In the copy activity's sink, change the file naming pattern to include a partition index, run ID, or timestamp to generate unique file names per parallel partition
- 3Use the 'Merge files' option only when a single output file is required, and limit parallelism to 1 for that activity
- 4Check for other pipelines or applications that might be writing to the same path and coordinate their schedules