Requesting clarification on Azure Advisor VM Rightsizing recommendations

Question

Requesting clarification on Azure Advisor VM Rightsizing recommendations

Anil Kumar 525

Hello,

We are analyzing VM Rightsizing recommendations generated by Azure Advisor with 90 days look back period and 100% CPU utilization in its configurations rules.

Could you please clarify following questions on ?

Does Azure Advisor take into consideration the count of disk attached to a VM while generating Rightsizing recommendation? If 17 disk are attached at present, will Azure recommend only VM sizes who can support at least 17 disks.
Does Azure Advisor takes into consideration the storage throughput: IOPS/MBps and Max uncached disk throughput: IOPS/MBps of VM target to ensure if equals to or greater than the max IOPS/MBps of VM current size in Rightsizing recommendation? If VM current size can support 25600 IOPS but max IOPS on that VM is only 6000 - Would Azure Advisor recommend VM sies which can support at least 6000 IOPS?
Does Azure Advisor takes into consideration the max or P95 max CPU usage of VMs while generating Rightsizing recommendation? Below article mentions:
1. Recommendation criteria include CPU, Memory and Outbound Network utilization.
  1. Metrics are sampled every 30 seconds, aggregated to 1 minute and then further aggregated to 30 minutes (taking the max of average values while aggregating to 30 minutes).

Not understanding how Azure Advisor can make right recommendations considering only AVG metrics utilizations.

I feel like executing Azure Advisor VM Rightsizing recommendations is very risky, are there any pointers that should we take into consideration to ensure target VM size is rightly sized.

https://learn.microsoft.com/en-us/azure/advisor/advisor-cost-recommendations

Applicate your Response. Thank you!!

Anil Kumar 525 Reputation points

2023-09-28T04:50:18.9466667+00:00

Could anyone please clarify if time permits?

Thank you!

Accepted answer

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Anil Kumar 525 Reputation points

2023-09-28T04:50:18.9466667+00:00

Could anyone please clarify if time permits?

Thank you!

Answer 1

vipullag-MSFT 26,492 Moderator

Hello Anil Kumar

Sharing responses for your queries:

-Does Azure Advisor takes into consideration the max or P95 max CPU usage of VMs while generating Rightsizing recommendation? Below article mentions:

Recommendation criteria include CPU, Memory and Outbound Network utilization.

Metrics are sampled every 30 seconds, aggregated to 1 minute and then further aggregated to 30 minutes (taking the max of average values while aggregating to 30 minutes).

Yes, Azure Advisor does take into consideration the maximum CPU utilization of the VMs while generating Rightsizing recommendations. The article you mentioned is correct that the metrics are sampled every 30 seconds, aggregated to 1 minute, and then further aggregated to 30 minutes (taking the max of average values while aggregating to 30 minutes). This means that Azure Advisor considers both the average and maximum CPU utilization of the VM over a 30-minute period to determine the VM usage.

The article you mentioned is also correct that the recommendation criteria include CPU, Memory, and Outbound Network utilization.

-Also how VM usage can be determined based on AVG metrics data - on one VM, I see CPU reaching 80% or more couple of times in a day but its AVG CPU utilization is very less?

Azure Advisor uses a combination of average and maximum values to determine VM usage. The metrics are sampled every 30 seconds, aggregated to 1 minute, and then further aggregated to 30 minutes (taking the max of average values while aggregating to 30 minutes). This means that Azure Advisor considers both the average and maximum CPU utilization of the VM over a 30-minute period to determine the VM usage.

In your example, if the CPU reaches 80% or more a couple of times in a day but the average CPU utilization is very low, it is possible that the high CPU utilization is occurring during peak usage periods. Azure Advisor takes this into account by considering the maximum CPU utilization over a 30-minute period, which would capture the peak usage periods.

I understand your concern about executing Azure Advisor VM Rightsizing recommendations based on average metrics utilization. While it is true that Azure Advisor uses average metrics utilization to generate recommendations, it also takes into account the maximum utilization over a 30-minute period. This means that Azure Advisor considers both the average and maximum CPU utilization of the VM over a 30-minute period to determine the VM usage.

Hope this clarifies.

Anil Kumar 525 Reputation points

2023-09-28T11:28:10.11+00:00

Thank you very much @vipullag-MSFT for your detailed response.

We cross checked and found Azure Advisor does take into consideration the number of disks attached to a VM while generating Rightsizing recommendations. We are good on this.

"Azure Advisor does take into consideration the storage throughput**:** IOPS/MBps and Max uncached disk throughput: IOPS/MBps of the target VM to ensure if it is equal to or greater than the max IOPS/MBps of the current VM size in Rightsizing recommendation." - We calculated the Max uncached disk IOPS and bandwidth by multiplying mentioned metrics utilization by max uncached IOPS and bandwidth of the VM and then compared this with max uncached IOPS and bandwidth of the target VM. Out of 24, we found 2 VMs where target VM size was small enough to support the IOPS and bandwidth requirements. We did convert % into numeric value for mention metrics after multiplication.

"metrics are sampled every 30 seconds, aggregated to 1 minute, and then further aggregated to 30 minutes (taking the max of average values while aggregating to 30 minutes). This means that Azure Advisor considers both the average and maximum CPU utilization of the VM over a 30-minute period to determine the VM usage." - Sorry, I couldn't get your point. Taking max of AVG may not necessarily be MAX. Let's assume there are 4 data points after calculating AVG, 10, 20, 30 and 20 - Max of given data points would be 30 but it might not relate with actual data point where CPU max might have been 80% before AVG was calculated. May be MAX itself could be misleading so we might need something like P95 or P90. .

"In your example, if the CPU reaches 80% or more a couple of times in a day but the average CPU utilization is very low, it is possible that the high CPU utilization is occurring during peak usage periods. Azure Advisor takes this into account by considering the maximum CPU utilization over a 30-minute period, which would capture the peak usage periods." - I would be grateful if there is some documentation about this point.

Could you please share with me if there is any official documentation on Azure Advisor indicating it takes into account CPU max, IOPS, throughput, etc. parameters or complete list of parameters? We can share same with colleagues and customers.

Request you to consider replying if your schedule permits and share the article/blog/white paper if any on Azure Advisor.

Thank you once again for your time.

#StayBlessednHappy
vipullag-MSFT 26,492 Reputation points Moderator

2023-09-29T04:00:22.9366667+00:00

Hello Anil Kumar

Thanks for responding on this, I would suggest that if you can connect with support team they can clarify more over a call. I would recommend you to open a azure support case.

If you don't have a support plan enabled on your subscription, I request you to send an email to AzCommunity@Microsoft.com with Subject as "Attn:Vikas" referencing this thread along with your subscription ID. I can then enable your subscription with a one-time free technical support.

Once your queries are clarified, request you to post the learning and details back here for the benefit of community.
Anil Kumar 525 Reputation points

2023-09-29T04:27:06.5766667+00:00

Thank you very much @vipullag-MSFT for your valued response.

I will create the support ticket and share the learning with the community.

Will keep the update posted.

#StayBlessednHappy
Anil Kumar 525 Reputation points

2023-09-29T06:15:03.7966667+00:00

Hello @vipullag-MSFT,

I have opened a support case.

If support engineer asks, can I point him to this conversation ?

Just asking your opinion.
Anil Kumar 525 Reputation points

2023-09-29T07:51:07.5133333+00:00

Sorry @vipullag-MSFT for bothering you. We got below response from support engineer. I didn't point him to this conversation...
Anil Kumar 525 Reputation points

2023-09-29T10:41:50.0066667+00:00

Just an update, support engineer is reviewing his answers..
vipullag-MSFT 26,492 Reputation points Moderator

2023-09-30T03:47:53.0533333+00:00

Hello Anil Kumar
Thanks for updating back here, support team will be able to check and clarify on this.
Anil Kumar 525 Reputation points

2023-10-10T03:47:35.56+00:00

Hello @vipullag-MSFT,

Support engineer checked with product team and provided following response.

"Azure Advisor cost recommendation algorithm does not take into account any other metrics apart from CPU, Memory and Network. So, disk count and disk IOPS are not considered while providing the next best size recommendation.
For example, if the size D3v2 is found idle or running on less load. it can suggest alternative size which is D2v3 which can be newer version. you need to manually check the number of disk new recommended disks supported or not."

Can I point him to this conversation ?

Just asking your opinion.
Anil Kumar 525 Reputation points

2023-10-13T13:55:08.5766667+00:00

Hello @vipullag-MSFT,

I had to point support engineer to this thread. I waited for your permission but you seems busy.

Today we opened another ticket for following issue.

We found couple of VMs with single digit CPU, Memory and Network utilization over 90 days but Azure Advisor didn't had any rightsizing recommendation for them. Getting to the point answers is becoming a bit difficult from support.

Thank you for your all time and help!

#StayBlessednHappy
Anil Kumar 525 Reputation points

2023-10-30T05:20:43.07+00:00

Hello @vipullag-MSFT,

We got following response from support engineer.

We got the confirmation from the PG that - We don’t currently support both (the count of disks & the storage throughput: IOPS/MBps and Max uncached disk throughput: IOPS/MBps) of those metrics yet on our model for generating recommendations.

Did any one reach out to you regarding this case or could you please share the source of information you had provided so I can share same with support engineer?

Appreciate your response. Thank you!
Anil Kumar 525 Reputation points

2023-11-01T07:01:57.45+00:00
Hello @vipullag-MSFT,

Thank you for all your help and support - We got better clarity on our questions.

Glad to mark your response as answer - Kindly keep helping the community if your time permits !

Our approach and understanding

Azure Advisor does not generate rightsizing recommendations for VMs which are running on schedules or running on request. I If look back period is set to 7 days, VM must be running for 6 days to be considered for rightsizing.

We fetched the matrices programmatically for the VMs for which there was no rightsizing recommendations and found many VMs suitable for rightsizing based on analyzing metrics data. To cross check the authenticity of your approach, we fetched metrics of VMs with rightsizing recommendations and compared them with Metrics captured in Azure advisor - numbers are quite close to each other.

While fetching metrics we got to know API has limitation of fetching just 30 days data - we have to make three calls in order to fetch the metrics of 90 days which was our look back period, I think same limitation is there in workbooks.

We can not rely on Azure Advisor projected cost saving so we had to find the current cost and then calculate target size cost to calculate the savings.

While generating VM rightsizing recommendations, Azure Advisor does not take into account the count of disks (Attached to VM currently and Disk supported by target VM size) & the storage throughput: IOPS/MBps (Max (P100/P95/P90) IOPS/MBps on current VM size and max IOPS/MBps supported by target VM size) and Max uncached disk throughput: IOPS/MBps). We found multiple line items in which Azure Advisor given target VM sizes didn't had adequate supported IOPS or MBps - executing such recommendations are risky. We had to manually change the target size to next higher size within the same family to make sure it has adequate IOPS/MBps.

Hope above information would be helpful to the community.

#StayBlessednHappy.

Answer 2

AirGordon 7,150

My experience is that the Advisor recommendations are a good starting place, but do not take into account many of the variables.

The docs do provide a comprehensive list of factors that are used in the recommendation: https://learn.microsoft.com/en-us/azure/advisor/advisor-cost-recommendations#resize-sku-recommendations

I'd suggest that you leverage standard practices like making changes and testing in representative non-prod environments before making changes to production environments to then build confidence that the recommendation is correct.

Anil Kumar 525 Reputation points

2023-09-25T04:40:15.83+00:00

Thank you @AirGordon for taking time to help, that too on weekends !!

I have already gone through the article and unfortunately it doesn't answer any if the questions I asked. In fact, I got those question while reading this article.

Could you please elaborate what are the variables that Advisor recommendations do not take into account?

Also how VM usage can be determined based on AVG metrics data - on one VM, I see CPU reaching 80% or more couple of times in a day but its AVG CPU utilization is very less?

Applicate your Response. Thank you!!

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Requesting clarification on Azure Advisor VM Rightsizing recommendations

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