What is the recommended minimum file size when working with external data on files in Microsoft Fabric?

• A. At least 4 MB.
• B. At least 1 MB.
• C. At least 10 MB.
• D. At least 16 MB.

Answer: (A)

When you work with external data on files in Microsoft Fabric, file size directly affects how efficiently the system can read and parallelize the data. Small files introduce a lot of metadata and I/O overhead relative to the data they contain, which can slow down queries and increase costs. A minimum of 4 MB per file provides enough data per file to amortize that overhead, enabling better throughput, more effective parallel processing, and efficient use of caching and storage layout. Files smaller than that tend to be excessively fragmented, causing many small read tasks and higher overhead. While larger files (such as 10 MB or 16 MB) can still work, the recommended floor is 4 MB because it gives a practical balance between file count and processing efficiency.