Understanding F4 Capacity in Microsoft Fabric

[Karen_Mendez2]

Hi everyone,

I’m working with an F4 capacity in Microsoft Fabric, but I have some doubts about how it works.

If I consume 100% of the capacity within half a day, does it renew automatically? If so, how often are the resources replenished?

I’d appreciate any clarification or resources to better understand this.

Thanks in advance!

[FabianSchut · Accepted solution]

Hi, if you buy an F4 capacity, you can consume 4 CU's during the entire period the F4 is active. In a world where no parallelization is active, this would mean that you could run 4 activities non-stop for the entire period. Even though you only have 4 CU available, Fabric can run 8 (and even more) activities at the same time. When this happens, it borrows 4 CU from the future. It can only borrow CU's that would normally be available in the next 24 hour. This would mean that if you have 8 activities for 12 hours, you cannot run any other activities for the next 12 hours. After 12 hours with no activities, you will automatically get CU's again and are able to run new activities. 

[Karen_Mendez2]

@FabianSchut 
Thank you for the explanation, it was very clear! 😊 I have another question: if I reach 100% capacity usage and decide to reset it, does this incur any additional cost?

[v-jingzhan-msft · Accepted solution]

Hi @Karen_Mendez2 

You may read the following articles:

Understand your Fabric capacity throttling - Microsoft Fabric

Pause and resume your capacity - Microsoft Fabric

In the second article, it says --

When you pause your capacity, the remaining cumulative overages and smoothed operations on your capacity are summed, and added to your Azure bill. You can monitor a paused capacity using the Microsoft Fabric Capacity Metrics app.

If your capacity is being throttled, pausing it stops the throttling and returns your capacity to a healthy state immediately. This behavior enables you to pause your capacity as a self-service mechanism that ends throttling.

If I understand it correctly, when you pause a capacity, the remaining cumulative CUs will be summed and added to your bill. In this run, the total cost includes the sum of the 4 CUs that F4 originally has and the remaining CUs that have not been smoothed.

When you restart the capacity, the CU calculation starts from the beginning. At this point, you can do operations without being throttled until the CU usage reaches 100% again, which will trigger new throttling and smoothing.

If my understanding is incorrect, please correct me. Hope this would be helpful. 

Best Regards,
Jing
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[FabianSchut · Accepted solution]

Hi, if you buy an F4 capacity, you can consume 4 CU's during the entire period the F4 is active. In a world where no parallelization is active, this would mean that you could run 4 activities non-stop for the entire period. Even though you only have 4 CU available, Fabric can run 8 (and even more) activities at the same time. When this happens, it borrows 4 CU from the future. It can only borrow CU's that would normally be available in the next 24 hour. This would mean that if you have 8 activities for 12 hours, you cannot run any other activities for the next 12 hours. After 12 hours with no activities, you will automatically get CU's again and are able to run new activities.