Understanding Azure Function App Consumption Plan and Blob Storage Costs (GPv1 vs GPv2)

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Understanding Azure Function App Consumption Plan and Blob Storage Costs (GPv1 vs GPv2)

DJ 70

Hi all,

I would appreciate some advice on how to structure my Azure Function App on a Consumption Plan correctly.

At the moment, I am using a Function App that is triggered whenever a message is received from Azure IoT Hub. The function analyses the incoming packet and performs the required operations based on the contents of that message.

My Function App is running on the Consumption Plan, and I believe it is currently using a General-Purpose v1 (GPv1) storage account for its underlying storage.

Recently, I received a notification suggesting that the storage account should be upgraded from General-Purpose v1 to General-Purpose v2 (GPv2). However, my concern is related to cost. From what I understand, GPv2 pricing can be higher depending on the type and number of storage transactions, and for this particular workload I need to keep costs as low as possible.

My understanding is that even though the Function App performs its execution internally, it still makes underlying API calls to Blob Storage for things such as logs, triggers, and state management. Because of this, I am wondering whether the Function App itself is generating a significant number of storage transactions behind the scenes.

From what I can see, the Blob Storage account is being used for several operations, which made me question whether the Function App relies more heavily on storage than I originally assumed.

So my questions are:

Am I correct in understanding that Azure Functions internally invoke Blob Storage APIs during execution?

Is the storage account mainly used for function state, logs, and trigger management, or is there something else happening behind the scenes?

Is upgrading to GPv2 unavoidable for Azure Function Apps, and how much impact does it typically have on costs? Is there a way to see the values for Write, Read, and other storage operations so that I can estimate what to expect in terms of charges? My storage account currently shows 96,328 transactions, so I assume this figure represents the combined total of read, write, and other operations. Is that correct?

I suspect I may have misunderstood the relationship between Azure Functions and the underlying storage account, as it appears to be doing more than just storing files.

Any guidance or clarification would be greatly appreciated.

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Pravallika KV 13,135 Microsoft External Staff Moderator

Hi @DJ,

Thanks for reaching out to Microsoft Q&A.

Do Azure Functions call Blob Storage APIs?

Yes. Even though your function code only fires on an IoT Hub event, the Functions runtime uses Blob (and Queue) Storage for several things under the covers:

Trigger/lease checkpointing (e.g. Event Hub or Blob triggers use blob leases and metadata)
Host metadata (function.json, extension bundles)
Logging (when you use file-based logs or the built-in file system logger)
Durable state (if you’re using Durable Functions)

What kinds of operations get generated?

You'll see a mix of ListBlob, GetBlobProperties, SetBlobMetadata, LeaseAcquire/Release, Write (for logs or state), etc. Your “96,328 transactions” is indeed the total of Reads + Writes + Other operations over the period you looked at.

GPv1 vs GPv2 and cost impact

You can keep using a GPv1 account today, but GPv2 is the current recommended platform. GPv2 gives you access to all the latest features (event-driven blob triggers, hierarchical namespace, advanced lifecycle policies, Azure AD auth hooks, etc.).

Pricing is per-transaction, so the difference in cost depends entirely on your transaction count and the tier (Hot/Cool). GPv1 didn’t charge for write operations in blob accounts, but GPv2 does, so if you do a lot of small writes (logs or leases) you will see some incremental cost.

How to see your read/write/other volumes

In the Azure portal, go to your Storage Account =>Metrics =>add the “Transactions by API name” and “Transactions by storage type” charts. That breaks down exactly which REST calls (GetBlobProperties, ListBlobs, PutBlockList, etc.) are happening and their counts.

If you need a CSV you can also turn on Storage Analytics (classic) or Diagnostics settings to send metrics to a Log Analytics workspace and then query it.

Cost estimation tips

Use the Azure Pricing Calculator (Storage Accounts tile) to plug in your transaction count (per 10,000 operations) and your GB/month of data storage.
In the portal under Cost Management + Billing =>Cost analysis you can filter on your storage account resource to see historical spend by meter (Data Storage, Transactions, Data Transfer).

References:

Hope this helps!

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DJ 70 Reputation points

2026-03-11T10:56:17.3+00:00

@Pravallika KV

Thank you for your reply

Have some additional questions,

When you mentioned

Logging (when you use file-based logs or the built-in file system logger)

Does this refer to the in-code command prompt–type logs? If so, what about Application Insights–type logs? I ask because my IoT Hub–triggered Function App will be triggered several hundred times per minute, so I would like to make it as efficient as possible.

As you mentioned, we can continue using GPv1. Will it still be supported beyond October 2026?

GPv1 didn’t charge for write operations in blob accounts, but GPv2 does, so if you do a lot of small writes (logs or leases) you will see some incremental cost.

How can we check what GPv2 would charge if we were to upgrade? For example, you mentioned that GPv1 does not charge for writes. Would logs be the only write operations in this case? Also, there are currently 96,328 operations. As the calculator shows reads, writes, and other operations with the same value, would it be correct to assume that this equates to around 10 units (10K operations)?

Using GPv2 purely for the purpose of a Function App, is there a minimum requirement for tier?
Pravallika KV 13,135 Reputation points Microsoft External Staff Moderator

2026-03-11T19:54:17.81+00:00
@DJ

Does this refer to the in-code command prompt–type logs?

Yes. Logs from things like:

log.LogInformation(...) Console.WriteLine(...)

If Azure Application Insights is enabled, those logs go there and do not create Blob storage writes.

Blob/file writes happen only if file logging is enabled.

As you mentioned, we can continue using GPv1. Will it still be supported beyond October 2026?

No, Azure Storage General Purpose v1 will be retired Oct 13, 2026, and if you do not migrate your general-purpose v1 storage account to GPv2 by October 2026, all existing general-purpose v1 accounts will be auto migrated over to a GPv2 account, which may result in higher billing costs. Your decision not to migrate an existing general-purpose v1 account will be construed as consent for Microsoft to migrate the account on your behalf.

How can we check what GPv2 would charge if we were to upgrade?

You can check the MSDOC regarding Pricing considerations when upgrading to GPv2.

Example: 96,328 operations Pricing uses units of 10,000 operations:

96,328 / 10,000 ≈ 9.6 ≈ ~10 units

So, you would enter ~10 transaction units in the Azure Pricing Calculator.

Are logs the only write operations?

No. Even without logs, Azure Functions writes for:

checkpoint updates (IoT/Event Hub trigger)

partition leases

runtime host locks

Minimum tier for GPv2 for Function Apps?

You can use below setup for Function Apps.

GPv2 Standard Hot tier LRS redundancy
DJ 70 Reputation points

2026-03-11T20:51:05.6366667+00:00

@Pravallika KV

Thank you. So would each log entry equate to a write operation on Blob Storage?

Yes, I have enabled Application Insights, but there is a limit on how much data I capture. Once that capture limit is reached, any additional logs are not saved. How would this affect the writes to Blob Storage?

Would the automated upgrade do anything different compared to performing the upgrade manually?

When we check the calculator, is there anything else we need to include in addition to the 96,328 transaction count?
Pravallika KV 13,135 Reputation points Microsoft External Staff Moderator

2026-03-12T00:43:06.1066667+00:00

Do log entries create Blob writes?

Only logs written by the Function runtime to storage (file-based or diagnostic logs) generate Blob writes. Application Insights logs, including ILogger calls, go through telemetry and do not touch Blob storage, so they won’t increase storage transactions.

In modern Function Apps, if you’re using Application Insights, normal logs (Info, Warning, Error) do not create Blob writes. The only writes are internal runtime operations, like checkpoints, leases, or secret storage.

Application Insights capture limit reached?

Hitting the Application Insights data cap only stops new telemetry from being stored in App Insights. It does not affect Blob storage writes, because runtime operations like checkpoints and leases continue independently of Application Insights logging.

Automated vs manual GPv2 upgrade?

Automated upgrade after GPv1 retirement seamlessly converts the account to GPv2 with default settings (Standard, Hot, LRS). Manual upgrade lets you choose tiering, replication, and performance options, giving slightly more control over costs and configuration.

Calculator – what to include?

Include all storage transactions (reads, writes, lists), the total data stored in GB, and the replication/tier configuration. Your 96,328 transactions are the main component; Application Insights logs are not part of this calculation.
DJ 70 Reputation points

2026-03-12T12:25:59.3533333+00:00
Thank You @Pravallika KV

Ok, how can I check that diagnostic logs or unnecessary data are not being returned? The aim is to avoid unnecessary API calls, especially if the data is not being used.

For calls such as checkpoints, leases, or secret storage, do we have any control over them from the Function App portal?

I use logs as shown

log.LogInformation($"Incoming Message {index}/{batchSize}: --> {IOTMESSAGE}");

Also, would it be best to manually perform the upgrade? I will plan to do this closer to the time.

At the moment there are 96,328 transactions. How can I verify that this does not include unnecessary logs? Are there any settings I can check in both the Azure Function App and Storage Account settings?

I understand that logs can be useful when debugging, but in this case I need to keep the costs as low as possible for this task. I want to make sure that, within the 96,328 transactions, there are no unnecessary operations being generated.
Pravallika KV 13,135 Reputation points Microsoft External Staff Moderator

2026-03-12T23:02:59.38+00:00
Your log.LogInformation(...) logs go to Azure Application Insights, not Blob storage, so they do NOT create storage transactions.

The 96,328 transactions you see are almost certainly normal runtime operations from Azure Functions (checkpoints, leases, host state) used by triggers like Azure IoT Hub.

Steps to verify no unnecessary logs are written to storage:

Function App =>Monitoring =>Diagnostic settings

Ensure logs are not sent to Storage Account (only to Application Insights).

Function App =>Monitoring =>App Service logs

Ensure Application Logging (Filesystem) = Off.

Storage Account =>Containers Normal containers: azure-webjobs-hosts, azure-webjobs-secrets, azure-webjobs-eventhub. If you see insights-logs or appservice-logs, those indicate logs being stored.

Control over checkpoints/leases: No, they are automatic runtime operations and cannot be disabled.

Upgrade: Manual upgrade to GPv2 is fine and recommended; cost impact at your transaction level will be negligible.
Pravallika KV 13,135 Reputation points Microsoft External Staff Moderator

2026-03-17T21:32:35.26+00:00

@DJ , If the above resolution was helpful, kindly take a moment to click on "Accept Answer" and click on Yes for was this answer helpful. And, if you have any further query do let us know

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Understanding Azure Function App Consumption Plan and Blob Storage Costs (GPv1 vs GPv2)

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