With growing popularity of the lakehouse there has been a rising interest in the analysis and comparison of the open source projects which are at the core of this data architecture: Apache Hudi, Delta Lake, and Apache Iceberg.
Most comparison articles currently published seem to evaluate these projects merely as table/file formats for traditional append-only workloads, overlooking some qualities and features that are critical for modern data lake platforms that need to support update heavy workloads with continuous table management. This article will dive into greater depth to highlight technical differentiators of Apache Hudi and how it is a full fledged data lake platform steps ahead of the rest.
This article is periodically updated to keep up with the fast moving landscape. The last update was in January 2023 which updated the feature comparison matrix, added in statistics about the community adoption, and referenced recent benchmarks that were published in the industry.
First let’s look at an overall feature comparison. As you read, notice how the Hudi community has invested heavily into comprehensive platform services on top of the lake storage format. While formats are critical for standardization and interoperability, table/platform services give you a powerful toolkit to easily develop and manage your data lake deployments.
Equally important to features and capabilities of an open source project is the community. The community can make or break the development momentum, ecosystem adoption, or the objectiveness of the platform. Below is a comparison of Hudi, Delta, Iceberg when it comes to their communities:
Github stars is a vanity metric that represents popularity more than contribution. Delta Lake leads the pack in awareness and popularity.
Github Watchers and Forks
A closer indication of engagement/usage of the project:
In December 2022 Apache Hudi had almost 90 unique authors contribute to the project. More than 2x Iceberg and 3x Delta Lake.
Github PRs and Issues
In December 2022 Hudi and Iceberg merged about the same # of PRs while the number of PRs opened was double in Hudi.
Apache Hudi and Apache Iceberg have a strong diversity in the community who contributes to the project.
Performance benchmarks rarely are representative of real life workloads, and we strongly encourage the community to run their own analysis against their own data. Nonetheless these benchmarks can serve as an interesting data point while you start your research into choosing a Lakehouse platform. Below are references to relevant benchmarks:
Databeans and Onehouse
Databeans worked with Databricks to publish a benchmark used in their Data+AI Summit Keynote in June 2022, but they misconfigured an obvious out-of-box setting. Onehouse corrected the benchmark here:
Brooklyn Data and Onehouse
Databricks asked Brooklyn Data to publish a benchmark of Delta vs Iceberg in Nov 2022:
Onehouse added Apache Hudi and published the code in the Brooklyn Github repo:
A clear pattern emerges from these benchmarks, Delta and Hudi are comparable, while Apache Iceberg consistently trails behind as the slowest of the projects. Performance isn’t the only factor you should consider, but performance does translate into cost savings that add up throughout your pipelines.
A note on running TPC-DS benchmarks:
One key thing to remember when running TPC-DS benchmarks comparing Hudi, Delta, Iceberg is that by default Delta + Iceberg are optimized for append-only workloads, while Hudi is by default optimized for mutable workloads. By default, Hudi uses an `upsert` write mode which naturally has a write overhead compared to inserts. Without this knowledge you may be comparing apples to oranges. Change this one out-of-the-box configuration to `bulk-insert` for a fair assessment: https://hudi.apache.org/docs/write_operations/
Building a data lake platform is more than just checkboxes of feature availability. Let’s pick a few of the differentiating features above and dive into the use cases and real benefits in plain english.
The majority of data engineers today feel like they have to choose between streaming and old-school batch ETL pipelines. Apache Hudi has pioneered a new paradigm called Incremental Pipelines. Out of the box, Hudi tracks all changes (appends, updates, deletes) and exposes them as change streams. With record level indexes you can more efficiently leverage these change streams to avoid recomputing data and just process changes incrementally. While other data lake platforms may enable a way to consume changes incrementally, Hudi is designed from the ground up to enable incrementalization efficiently which results in cost efficient ETL pipelines at lower latencies.
Databricks recently developed a similar feature they call Change Data Feed which they have held proprietary until it was finally released to open source in Delta Lake 2.0. Iceberg has an incremental read, but it only allows you to read incremental appends, no updates/deletes which are essential for true Change Data Capture and transactional data.
ACID transactions and concurrency control are key characteristics of a Lakehouse, but how do current designs actually stack up compared to real world workloads? Hudi, Delta, and Iceberg all support Optimistic Concurrency Control (OCC). In optimistic concurrency control, writers check if they have overlapping files and if a conflict exists, they fail the operations and retry. For Delta Lake as an example this was just a JVM level lock held on a single Apache Spark driver node which means you have no OCC outside of a single cluster, until recently.
While this may work fine for append-only immutable datasets, optimistic concurrency control struggles with real world scenarios which introduces the need for frequent updates and deletes because of the data loading pattern or reorganizing the data for query performance. Oftentimes, it’s not practical to take writers offline for table management to ensure the table is healthy and performant. Apache Hudi concurrency control is more granular than other data lake platforms (File level) and with a design optimized for multiple small updates/deletes the conflict possibility can be largely reduced to negligible in most real world cases. You can read more details in this blog, of how you can operate with asynchronous table services even in multi-writer scenarios, without the need to pause writers. This is very close to the level of concurrency supported by standard databases.
Merge On Read
Any good database system supports different trade-offs between write and query performance. The Hudi community has made some seminal contributions, in terms of defining these concepts for data lake storage across the industry. Hudi, Delta, and Iceberg all write and store data in parquet files. When updates occur, these parquet files are versioned and rewritten. This write mode pattern is what the industry now calls Copy On Write (CoW). This model works well for optimizing query performance, but can be limiting for write performance and data freshness. In addition to CoW, Apache Hudi supports another table storage layout called Merge On Read (MoR). MoR stores data using a combination of columnar parquet files and row-based Avro log files. Updates can be batched up in log files that can later be compacted into new parquet files synchronously or asynchronously to balance maximum query performance and lower write amplification.
Thus, for a near real time streaming workload, Hudi could use the more efficient row oriented formats and for batch workloads the hudi format uses vectorizable column oriented format with seamless merging of the two formats when required. Many users turn to Apache Hudi since it is the only project with this capability which allows them to achieve unmatched write performance and E2E data pipeline latencies.
One feature often highlighted for Apache Iceberg is hidden partitioning that unlocks what is called partition evolution. The basic idea is when your data starts to evolve, or you just aren’t getting the performance value you need out of your current partitioning scheme, partition evolution allows you to update your partitions for new data without rewriting your data. When you evolve your partitions, old data is left in the old partitioning scheme and only new data is partitioned with your evolution. A table partitioned multiple ways pushes complexity to the user and cannot guarantee consistent performance if the user is unaware of the evolution history.
Apache Hudi takes a different approach to address the problem of adjusting data layout as your data evolves with Clustering. You can choose a coarse-grained partition strategy or even leave it unpartitioned, and use a more fine-grained clustering strategy within each partition. Clustering can be run synchronously or asynchronously and can be evolved without rewriting any data. This approach is comparable to the micro-partitioning and clustering strategy of Snowflake.
Indexing is an integral component for databases and data warehouses, yet is largely absent in data lakes. In recent releases, Apache Hudi created a first-of-its-kind high performance indexing subsystem for the Lakehouse that we call the Hudi Multi-Modal Index. Apache Hudi offers an asynchronous indexing mechanism that allows you to build and change indexes without impacting write latency. This indexing mechanism is extensible and scalable to support any popular index techniques such as Bloom, Hash, Bitmap, R-tree, etc.
These indexes are stored in the Hudi Metadata Table which is stored in cloud storage next to your data. In this new release the metadata is written in optimized indexed file formats which results in 10-100x performance improvements for point lookups versus Delta or Iceberg generic file formats. When testing real world workloads, this new indexing subsystem results in 10-30x overall query performance.
What sets a data platform apart from data formats are the operational services available. A differentiator for Apache Hudi is the powerful ingestion utility called DeltaStreamer. DeltaStreamer is battle tested and used in production to build some of the largest data lakes on the planet today. DeltaStreamer is a standalone utility which allows you to incrementally ingest upstream changes from a wide variety of sources such as DFS, Kafka, database changelogs, S3 events, JDBC, and more.
Iceberg has no solution for a managed ingestion utility, and Delta Autoloader remains a Databricks proprietary feature that only supports cloud storage sources such as S3.
Feature comparisons and benchmarks can help newcomers orient themselves on what technology choices are available, but more important is sizing up your personal use cases and workloads to find the right fit for your data architecture. All three of these technologies, Hudi, Delta, Iceberg have different origin stories and advantages for certain use cases. Iceberg was born at Netflix and was designed to overcome cloud storage scale problems like file listings. Delta was born at Databricks and it has deep integrations and accelerations when using the Databricks Spark runtime. Hudi was born at Uber to power petabyte scale data lakes in near real-time, with painless table management.
From years of engaging in real world comparison evaluations in the community, Apache Hudi routinely has a technical advantage when you have mature workloads that grow beyond simple append-only inserts. Once you start processing many updates, start adding real concurrency, or attempt to reduce the E2E latency of your pipelines, Apache Hudi stands out as the industry leader in performance and feature set.
Here are a couple examples and stories from the community who independently evaluated and decided to use Apache Hudi:
“One of the biggest challenges ATS faced was handling data at petabyte scale with the need for constant inserts, updates, and deletes with minimal time delay, which reflects real business scenarios and package movement to downstream data consumers.”
“In this post, we show how we ingest data in real time in the order of hundreds of GBs per hour and run inserts, updates, and deletes on a petabyte-scale data lake using Apache Hudi tables loaded using AWS Glue Spark jobs and other AWS server-less services including AWS Lambda, Amazon Kinesis Data Firehose, and Amazon DynamoDB”
“In our scenario, the performance challenges are huge. The maximum data volume of a single table reaches 400PB+, the daily volume increase is PB level, and the total data volume reaches EB level.”
“The throughput is relatively large. The throughput of a single table exceeds 100 GB/s, and the single table needs PB-level storage. The data schema is complex. The data is highly dimensional and sparse. The number of table columns ranges from 1,000 to 10,000+. And there are a lot of complex data types.”
“When making the decision on the engine, we examine three of the most popular data lake engines, Hudi, Iceberg, and DeltaLake. These three have their own advantages and disadvantages in our scenarios. Finally, Hudi is selected as the storage engine based on Hudi’s openness to the upstream and downstream ecosystems, support for the global index, and customized development interfaces for certain storage logic.”
From video transcription:
“Okay so what is it that enables us for us and why do we really like the Hudi features that have unlocked this in other use cases? We like the optimistic concurrency or mvcc controls that are available to us. We’ve done a lot of work around asynchronous compaction. We’re in the process of looking at doing asynchronous compaction rather than inline compaction on our merge on read tables.
We also want to reduce latency and so we leverage merge on read table significantly because that enables us to append data much faster. We also love native support for deletion. It’s something we had custom frameworks built for things like ccpa and gdpr where somebody would uh put in a service desk ticket and we’d have to build an automation flow to remove records from hdfs this comes out of the box for us.
Row versioning is really critical obviously a lot of our pipelines have out of order data and we need the latest records to show up and so we provide version keys as part of our framework for all upserts into the hudi tables.
The fact that customers can pick and choose how many versions of a row to keep be able to provide snapshot queries and get incremental updates like what’s been updated in the last five hours is really powerful for a lot of users”
“Robinhood has a genuine need to keep data freshness low for the Data Lake. Many of the batch processing pipelines that used to run on daily cadence after or before market hours had to be run at hourly or higher frequency to support evolving use-cases. It was clear we needed a faster ingestion pipeline to replicate online databases to the data-lake.”
“We are using Apache Hudi to incrementally ingest changelogs from Kafka to create data-lake tables. Apache Hudi is a unified Data Lake platform for performing both batch and stream processing over Data Lakes. Apache Hudi comes with a full-featured out-of-box Spark based ingestion system called Deltastreamer with first-class Kafka integration, and exactly-once writes. Unlike immutable data, our CDC data have a fairly significant proportion of updates and deletes. Hudi Deltastreamer takes advantage of its pluggable, record-level indexes to perform fast and efficient upserts on the Data Lake table.”
“The Data Lake pipelines consolidate the data from Zendesk’s highly distributed databases into a data lake for analysis.
Zendesk uses Amazon Database Migration Service (AWS DMS) for change data capture (CDC) from over 1,800 Amazon Aurora MySQL databases in eight AWS Regions. It detects transaction changes and applies them to the data lake using Amazon EMR and Hudi.
Zendesk ticket data consists of over 10 billion events and petabytes of data. The data lake files in Amazon S3 are transformed and stored in Apache Hudi format and registered on the AWS Glue catalog to be available as data lake tables for analytics querying and consumption via Amazon Athena.”
“The introduction of a more seamless Apache Hudi experience within AWS has been a big win for our team. We’ve been busy incorporating Hudi into our CDC transaction pipeline and are thrilled with the results. We’re able to spend less time writing code managing the storage of our data, and more time focusing on the reliability of our system. This has been critical in our ability to scale. Our development pipeline has grown beyond 10,000 tables and more than 150 source systems as we approach another major production cutover.”
Finally, given how quickly lakehouse technologies are evolving, it’s important to consider where open source innovation in this space has come from. Below are a few foundational ideas and features that originated in Hudi and that are now being adopted into the other projects.
In fact, outside of the table metadata (file listings, column stats) support, the Hudi community has pioneered most of the other critical features that make up today’s lakehouses. The community has supported over 1500 user issues and 5500+ slack support threads over the last 4 years, and is rapidly growing stronger with an ambitious vision ahead. Users can consider this track record of innovation as a leading indicator for the future that lies ahead.
When choosing the technology for your Lakehouse it is important to perform an evaluation for your own personal use cases. Feature comparison spreadsheets and benchmarks should not be the end-all deciding factor, so we hope that this blog post simply provides a starting point and reference for you in your decision making process. Apache Hudi is innovative, battle hardened and here to stay. Join us on Hudi Slack where you can ask questions and collaborate with the vibrant community from around the globe.
If you would like 1:1 consultation to dive deep into your use cases and architecture, feel free to reach out at firstname.lastname@example.org. At Onehouse we have decades of experience designing, building, and operating some of the largest distributed data systems in the world. We recognize these technologies are complex and rapidly evolving. It is likely we missed a feature or could have read the documentation wrong on some of the above comparisons. Please drop a note to email@example.com if you see any comparisons above that stand in need of correction so we can keep the facts accurate in this article.