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

Hi @DJ,

Thanks for reaching out to Microsoft Q&A.

1. 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)

2. 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.

3. 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.

4. 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.

5. 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).

Hope this helps!

References:

• Plan and manage costs for Blob Storage
• Azure Blob Storage pricing
• Azure Functions storage considerations
• Consumption plan billing & GB-second costs
• View Storage metrics in the portal
• Cost analysis in Azure Cost Management

@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?

@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

@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?

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.