Dual Storage mode

[powerbiexpert22]

i am trying to understand dual storage mode in Power BI. I have gone through below document however I am not clear in which scenario I should use dual storage mode in Power BI , also I want to know are the limitations that I need to consider before using or applyig dual storage mode in Power BI 

https://learn.microsoft.com/en-us/power-bi/transform-model/desktop-storage-mode

[anmolmalviya05 · Accepted solution]

Hi @powerbiexpert22 ,

In Power BI, the Dual Storage Mode is one of three storage modes (alongside Import and DirectQuery). Dual mode allows a table to act as both Import and DirectQuery, depending on the context in which the table is used.

Key Characteristics of Dual Storage Mode:

Flexibility: Dual-mode tables can act as Import for performance-intensive queries and as DirectQuery for real-time or query-specific needs.

Hybrid Functionality: Power BI decides whether to query the local in-memory copy (Import) or directly query the data source (DirectQuery), depending on the relationships and query context.

When to Use Dual Storage Mode

Here are common scenarios where Dual Storage Mode is beneficial:

Hybrid Models:

When combining Import and DirectQuery tables in the same model.

For example, you have a large historical dataset in Import mode but want real-time updates for the current quarter using DirectQuery. Using Dual mode allows shared dimension tables to optimize performance.

Shared Dimensions:

When dimension tables (e.g., Date, Product, Customer) are shared between Import and DirectQuery fact tables.

In such cases, Dual mode allows these tables to adapt dynamically:

Use Import mode for queries involving Import fact tables (faster performance).

Use DirectQuery for queries involving DirectQuery fact tables (real-time data).

Optimizing Model Performance:

When you want to avoid redundant storage of dimension tables (which may already exist in Import mode) while ensuring DirectQuery works efficiently.

Example: A Calendar table that is accessed by both real-time DirectQuery fact tables and pre-loaded Import fact tables.

Reducing Data Refresh Time:

If a table is only occasionally required for real-time queries, Dual mode ensures it doesn't need to be fully loaded during data refresh.

Limitations of Dual Storage Mode

Before applying Dual Storage Mode, consider these limitations:

Memory Usage:

Since Dual mode also includes an Import copy, it consumes additional memory compared to DirectQuery alone.

Data Source Compatibility:

Dual mode depends on DirectQuery functionality. If the data source does not support DirectQuery, Dual mode cannot be used.

Query Performance Trade-offs:

While Dual mode is flexible, real-time queries still depend on the performance of the underlying DirectQuery source. Queries involving DirectQuery may experience latency compared to Import mode.

Complex Relationships:

Dual mode might not always work seamlessly with complex model relationships. For example, if there are ambiguous paths or many-to-many relationships, query execution can be inefficient.

Configuration Complexity:

Choosing when and where to apply Dual mode adds complexity to the model design. Careful planning is needed to ensure Dual mode provides the intended performance benefit.

[BI_Maverick]

In Power BI, when you connect to your data, you can choose how that data is stored — either Import (which brings a copy of the data into Power BI) or DirectQuery (which leaves the data in the source and queries it live when you interact with the report). Dual mode is kind of like having the best of both worlds. It allows a table to act like Import and DirectQuery depending on the situation.

You'd use dual mode mostly when you're mixing both Import and DirectQuery in the same report. For example, imagine your sales data is huge and stored in a data warehouse, so you connect using DirectQuery to avoid importing gigabytes of data. But you also have smaller tables like a calendar or product lookup, which are used to slice and filter your sales data. These smaller tables are better off as Import because they’re fast, don’t change much, and can help improve performance. By setting them to dual, Power BI can use the Import copy when possible (like when filtering visuals using slicers), and switch to DirectQuery only when needed.

The main benefit is performance. Instead of triggering live queries every time you interact with a slicer or filter, Power BI can use the in-memory data for those dual tables to make things snappy.

But there are a few things to watch out for. First, dual storage only makes sense when you're using both Import and DirectQuery in the same model. If you're using only Import or only DirectQuery, setting a table to dual won’t really help. Second, it can add complexity. Power BI has to decide when to use Import vs DirectQuery, and sometimes that logic isn’t obvious. If you're not careful, you might accidentally end up sending more live queries to your data source than you expected. That can slow things down, especially if your data source isn’t optimized.

TLDR: Use dual mode when you're mixing DirectQuery and Import, and want to boost performance by keeping your slicers and filter tables in memory. Just keep an eye on performance and make sure your model logic is clear. Let me know if you want an example scenario to make it even easier to picture.

If you like the solution, you can give kudos to my solution. Thanks. Happy learning Power BI

[powerbiexpert22]

Hi @anmolmalviya05 ,

i can use composite models in case of hybrid models , i am not clear on when i should use it, can you provide more explanation with example?

[Anonymous · Accepted solution]

Hi, @powerbiexpert22 

Composite Models: Composite models in Power BI allow you to combine multiple data sources into a single model. This means you can have both DirectQuery and Import data sources in the same report. 

When to Use Composite Models:

When you need to combine data from different sources, such as a mix of DirectQuery and Import data.
When you want to leverage the strengths of both DirectQuery (real-time data access) and Import (better performance for historical data).
When you need to create complex reports that require data from multiple sources.
Example: Imagine you are building a sales report. You have real-time sales data in a SQL Server database (DirectQuery) and historical sales data in an Excel file (Import). Using a composite model, you can combine these data sources into a single report, allowing you to analyze both real-time and historical sales data together.

Use composite models in Power BI Desktop - Power BI | Microsoft Learn

https://visiochart.com/blog/hybrid-vs-composite-models-in-power-bi/ 

Best Regards,

Community Support Team _Charlotte

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

[anmolmalviya05 · Accepted solution]

Hi @powerbiexpert22 ,

In Power BI, the Dual Storage Mode is one of three storage modes (alongside Import and DirectQuery). Dual mode allows a table to act as both Import and DirectQuery, depending on the context in which the table is used.

Key Characteristics of Dual Storage Mode:

Flexibility: Dual-mode tables can act as Import for performance-intensive queries and as DirectQuery for real-time or query-specific needs.

Hybrid Functionality: Power BI decides whether to query the local in-memory copy (Import) or directly query the data source (DirectQuery), depending on the relationships and query context.

When to Use Dual Storage Mode

Here are common scenarios where Dual Storage Mode is beneficial:

Hybrid Models:

When combining Import and DirectQuery tables in the same model.

For example, you have a large historical dataset in Import mode but want real-time updates for the current quarter using DirectQuery. Using Dual mode allows shared dimension tables to optimize performance.

Shared Dimensions:

When dimension tables (e.g., Date, Product, Customer) are shared between Import and DirectQuery fact tables.

In such cases, Dual mode allows these tables to adapt dynamically:

Use Import mode for queries involving Import fact tables (faster performance).

Use DirectQuery for queries involving DirectQuery fact tables (real-time data).

Optimizing Model Performance:

When you want to avoid redundant storage of dimension tables (which may already exist in Import mode) while ensuring DirectQuery works efficiently.

Example: A Calendar table that is accessed by both real-time DirectQuery fact tables and pre-loaded Import fact tables.

Reducing Data Refresh Time:

If a table is only occasionally required for real-time queries, Dual mode ensures it doesn't need to be fully loaded during data refresh.

Limitations of Dual Storage Mode

Before applying Dual Storage Mode, consider these limitations:

Memory Usage:

Since Dual mode also includes an Import copy, it consumes additional memory compared to DirectQuery alone.

Data Source Compatibility:

Dual mode depends on DirectQuery functionality. If the data source does not support DirectQuery, Dual mode cannot be used.

Query Performance Trade-offs:

While Dual mode is flexible, real-time queries still depend on the performance of the underlying DirectQuery source. Queries involving DirectQuery may experience latency compared to Import mode.

Complex Relationships:

Dual mode might not always work seamlessly with complex model relationships. For example, if there are ambiguous paths or many-to-many relationships, query execution can be inefficient.

Configuration Complexity:

Choosing when and where to apply Dual mode adds complexity to the model design. Careful planning is needed to ensure Dual mode provides the intended performance benefit.