Tackling the Small File Problem in Apache Iceberg

The modern data stack constantly evolves, with new technologies promising to solve age-old problems like scalability, cost, and data silos. Apache Iceberg, an open table format, has recently generated significant buzz. But is it truly revolutionary, or is it destined to repeat the pitfalls of past solutions like Hadoop?

In a recent episode of the Data Engineering Weekly podcast, we delved into this question with Daniel Palma, Head of Marketing at Estuary and a seasoned data engineer with over a decade of experience. Danny authored a thought-provoking article comparing Iceberg to Hadoop, not on a purely technical level, but in terms of their hype cycles, implementation challenges, and the surrounding ecosystems. This blog post expands on that insightful conversation, offering a critical look at Iceberg's potential and the hurdles organizations face when adopting it.

Hadoop: A Brief History Lesson

For those unfamiliar with Hadoop's trajectory, it's crucial to understand the context. In the mid-2000s, Hadoop emerged as a groundbreaking solution for processing massive datasets. It promised to address key pain points:

* Scaling: Handling ever-increasing data volumes.

* Cost: Reducing storage and processing expenses.

* Speed: Accelerating data insights.

* Data Silos: Breaking down barriers between data sources.

Hadoop achieved this through distributed processing and storage, using a framework called MapReduce and the Hadoop Distributed File System (HDFS). However, while the promise was alluring, the reality proved complex. Many organizations struggled with Hadoop's operational overhead, leading to high failure rates (Gartner famously estimated that 80% of Hadoop projects failed). The complexity stemmed from managing distributed clusters, tuning configurations, and dealing with issues like the "small file problem."

Iceberg: The Modern Contender

Apache Iceberg enters the scene as a modern table format designed for massive analytic datasets. Like Hadoop, it aims to tackle scalability, cost, speed, and data silos. However, Iceberg focuses specifically on the table format layer, offering features like:

* Schema Evolution: Adapting to changing data structures without rewriting tables.

* Time Travel: Querying data as it existed at a specific time.

* ACID Transactions: Ensuring data consistency and reliability.

* Partition Evolution: Changing data partitioning without breaking existing queries.

Iceberg's design addresses Hadoop's shortcomings, particularly data consistency and schema evolution. But, as Danny emphasizes, an open table format alone isn't enough.

The Ecosystem Challenge: Beyond the Table Format

Iceberg, by itself, is not a complete solution. It requires a surrounding ecosystem to function effectively. This ecosystem includes:

* Catalogs: Services that manage metadata about Iceberg tables (e.g., table schemas, partitions, and file locations).

* Compute Engines: Tools that query and process data stored in Iceberg tables (e.g., Trino, Spark, Snowflake, DuckDB).

* Maintenance Processes: Operations that optimize Iceberg tables, such as compacting small files and managing metadata.

The ecosystem is where the comparison to Hadoop becomes particularly relevant. Hadoop also had a vast ecosystem (Hive, Pig, HBase, etc.), and managing this ecosystem was a significant source of complexity. Iceberg faces a similar challenge.

Operational Complexity: The Elephant in the Room

Danny highlights operational complexity as a major hurdle for Iceberg adoption. While the Iceberg itself simplifies some aspects of data management, the surrounding ecosystem introduces new challenges:

* Small File Problem (Revisited): Like Hadoop, Iceberg can suffer from small file problems. Data ingestion tools often create numerous small files, which can degrade performance during query execution. Iceberg addresses this through table maintenance, specifically compaction (merging small files into larger ones). However, many data ingestion tools don't natively support compaction, requiring manual intervention or dedicated Spark clusters.

* Metadata Overhead: Iceberg relies heavily on metadata to track table changes and enable features like time travel. If not handled correctly, managing this metadata can become a bottleneck. Organizations need automated processes for metadata cleanup and compaction.

* Catalog Wars: The catalog choice is critical, and the market is fragmented. Major data warehouse providers (Snowflake, Databricks) have released their flavors of REST catalogs, leading to compatibility issues and potential vendor lock-in. The dream of a truly interoperable catalog layer, where you can seamlessly switch between providers, remains elusive.

* Infrastructure Management: Setting up and maintaining an Iceberg-based data lakehouse requires expertise in infrastructure-as-code, monitoring, observability, and data governance. The maintenance demands a level of operational maturity that many organizations lack.

Key Considerations for Iceberg Adoption

If your organization is considering Iceberg, Danny stresses the importance of careful planning and evaluation:

* Define Your Use Case: Clearly articulate your specific needs. Are you prioritizing performance, cost, or both? What are your data governance and security requirements? Your answers will influence your choices for storage, computing, and cataloging.

* Evaluate Compatibility: Ensure your existing infrastructure and tools (query engines, data ingestion pipelines) are compatible with Iceberg and your chosen catalog.

* Consider Cloud Vendor Lock-in: Be mindful of potential lock-in, especially with catalogs. While Iceberg is open, cloud providers have tightly coupled implementation specific to their ecosystem.

* Build vs. Buy: Decide whether you have the resources to build and maintain your Iceberg infrastructure or if a managed service is better. Many organizations prefer to outsource table maintenance and catalog management to avoid operational overhead.

* Talent and Expertise: Do you have the in-house expertise to manage Spark clusters (for compaction), configure query engines, and manage metadata? If not, consider partnering with consultants or investing in training.

* Start the Data Governance Process: Don't wait until the last minute to build the data governance framework. You must create the framework and processes before jumping into adoption.

The Catalog Conundrum: Beyond Structured Data

The role of the catalog is evolving. Initially, catalogs focused on managing metadata for structured data in Iceberg tables. However, the vision is expanding to encompass unstructured data (images, videos, audio) and AI models. This "catalog of catalogs" or "uber catalog" approach aims to provide a unified interface for accessing all data types.

The benefits of a unified catalog are clear: simplified data access, consistent semantics, and easier integration across different systems. However, building such a catalog is complex, and the industry is still grappling with the best approach.

S3 Tables: A New Player?

Amazon's recent announcement of S3 Tables raised eyebrows. These tables combine object storage with a table format, offering a highly managed solution. However, they are currently limited in terms of interoperability. They don't support external catalogs, making integrating them into existing Iceberg-based data stacks difficult. The jury is still unsure whether S3 Tables will become a significant player in the open table format landscape.

Query Engine Considerations

Choosing the right query engine is crucial for performance and cost optimization. While some engines like Snowflake boast excellent performance with Iceberg tables (with minimal overhead compared to native tables), others may lag. Factors to consider include:

* Performance: Benchmark different engines with your specific workloads.

* Cost: Evaluate the cost of running queries on different engines.

* Scalability: Ensure the engine can handle your anticipated data volumes and query complexity.

* Compatibility: Verify compatibility with your chosen catalog and storage layer.

* Use Case: Different engines excel at different tasks. Trino is popular for ad-hoc queries, while DuckDB is gaining traction for smaller-scale analytics.

Is Iceberg Worth the Pain?

The ultimate question is whether the benefits of Iceberg outweigh the complexities. For many organizations, especially those with limited engineering resources, fully managed solutions like Snowflake or Redshift might be a more practical starting point. These platforms handle the operational overhead, allowing teams to focus on data analysis rather than infrastructure management.

However, Iceberg can be a compelling option for organizations with specific requirements (e.g., strict data residency rules, a need for a completely open-source stack, or a desire to avoid vendor lock-in). The key is approaching adoption strategically, clearly understanding the challenges, and a plan to address them.

The Future of Table Formats: Consolidation and Abstraction

Danny predicts consolidation in the table format space. Managed service providers will likely bundle table maintenance and catalog management with their Iceberg offerings, simplifying the developer experience. The next step will be managing the compute layer, providing a fully end-to-end data lakehouse solution.

Initiatives like Apache XTable aim to provide a standardized interface on top of different table formats (Iceberg, Hudi, Delta Lake). However, whether such abstraction layers will gain widespread adoption remains to be seen. Some argue that standardizing on a single table format is a simpler approach.

Iceberg's Role in Event-Driven Architectures and Machine Learning

Beyond traditional analytics, Iceberg has the potential to contribute significantly to event-driven architectures and machine learning. Its features, such as time travel, ACID transactions, and data versioning, make it a suitable backend for streaming systems and change data capture (CDC) pipelines.

Unsolved Challenges

Several challenges remain in the open table format landscape:

* Simplified Data Ingestion: Writing data into Iceberg is still unnecessarily complex, often requiring Spark clusters. Simplifying this process is crucial for broader adoption.

* Catalog Standardization: The lack of a standardized catalog interface hinders interoperability and increases the risk of vendor lock-in.

* Developer-Friendly Tools: The ecosystem needs more developer-friendly tools for managing table maintenance, metadata, and query optimization.

Conclusion: Proceed with Caution and Clarity

Apache Iceberg offers a powerful approach to building modern data lakehouses. It addresses many limitations of previous solutions like Hadoop, but it's not a silver bullet. Organizations must carefully evaluate their needs, resources, and operational capabilities before embarking on an Iceberg journey.

Start small, test thoroughly, automate aggressively, and prioritize data governance. Organizations can unlock their potential by approaching Iceberg adoption cautiously and clearly while avoiding the pitfalls plaguing earlier data platform initiatives. The future of the data lakehouse is open, but the path to get there requires careful navigation.

All rights reserved ProtoGrowth Inc, India. I have provided links for informational purposes and do not suggest endorsement. All views expressed in this newsletter are my own and do not represent current, former, or future employers’ opinions.

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