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How to correctly calculate the capacity buffer in Autoscale


Alexandre Beaudoin1709160213

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Good day.

I have searched online, and I cannot find a way to correctly calculate the capacity buffer in Autoscale, so machines could turn on automatically if needed.  The default, at 10%, doesn't seem to do anything.  Right now I've decided to double it to 20% to see if it does anything, but it hasn't yet.

 

After about 12 or 13 users, my VDA servers start to experience issues.  Therefore, I'd like to have other servers turned on before I get to that number.

 

The old Smart Scale made sense, and I could go by number of Users.  The new autoscale doesn't seem to make sense, when I look at the load index in Director.  The load index for a server with about 12 users is usually about 5%.  It doesn't seem to be saying the CPU or memory is impacted, everything except the number of users is at 0.  

 

My farm is entirely in Azure, could this be the cause?

 

Please help me understand how the capacity buffer in autoscale works!

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On 2/24/2020 at 10:40 PM, Alexandre Beaudoin1709160213 said:

Good day.

I have searched online, and I cannot find a way to correctly calculate the capacity buffer in Autoscale, so machines could turn on automatically if needed.  The default, at 10%, doesn't seem to do anything.  Right now I've decided to double it to 20% to see if it does anything, but it hasn't yet.

 

After about 12 or 13 users, my VDA servers start to experience issues.  Therefore, I'd like to have other servers turned on before I get to that number.

 

The old Smart Scale made sense, and I could go by number of Users.  The new autoscale doesn't seem to make sense, when I look at the load index in Director.  The load index for a server with about 12 users is usually about 5%.  It doesn't seem to be saying the CPU or memory is impacted, everything except the number of users is at 0.  

 

My farm is entirely in Azure, could this be the cause?

 

Please help me understand how the capacity buffer in autoscale works!

Hi,

 

Did you configure "maximum numer of sessions" policy setting?

This is important to calculate the load.

 

Regards

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Hi!

Sounds more like you're missing configuration for load index and that your questions are regarding to that.

However, the AutoScale calculations are based on load index. Therefore your load configuration is interesting as the previous post says.

AutoScale calculations (Capacity buffer) work like this:
- Total load index in use: 32k 

- Total machines in the Delivery group: 10 (100k load if default max load per machine is 10000)

- Total machines as part of schedule based scaling – 3 (30kload index if default max load per machine is 10k)
- Capacity buffer: 10% (10k load index)

To honor buffer capacity (which is 10k - 1 machine in load index) – 42,000 capacity is needed in terms of load index.
5 machines needs to be powered on (If default load is 10k) -  If 4 machines are powered on they would not be able to accommodate the load index of 10k + the current user load of ~32k load.

 

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