Databricks Runtime 9.1 LTS and 10.4 LTS are both long-term support (LTS) versions, meaning they receive extended support and maintenance compared to non-LTS releases. However, there are key differences between the two versions:

Databricks Runtime 9.1 LTS:

• Release Date: September 2021
• End of Support: September 2024
• Apache Spark Version: 3.1.2
• Key Features:
  • Improved performance and stability
  • Enhanced security features
  • Support for newer Python and R libraries
  • Integration with Delta Lake

Databricks Runtime 10.4 LTS:

• Release Date: March 2022
• End of Support: March 2025
• Apache Spark Version: 3.2.1
• Key Features:
  • Photon (Public Preview) for accelerated performance
  • Iceberg to Delta table converter (Public Preview)
  • Auto Compaction rollbacks enabled by default
  • Low Shuffle Merge enabled by default
  • Improved support for Delta Lake features

Choosing the right version:

• If you prioritize stability and require compatibility with older libraries or tools, Databricks Runtime 9.1 LTS might be a better choice.
• If you need the latest features and performance enhancements, especially those related to Delta Lake and Photon, Databricks Runtime 10.4 LTS is a better option.

Additional Considerations:

• Check the compatibility of your existing code and libraries with both versions before upgrading.
• Consider the specific requirements of your workloads and use cases.