Azure Blob Storage Smart Tier is Officially Released — Automatic Cost Optimization Mechanism and Implementation Procedure

Azure Blob Storage’s Smart Tier has been officially released, enabling automatic cost optimization based on data access patterns. According to Aung Oo from the Microsoft Azure Storage team, during the preview period, over 50% of the capacity managed by Smart Tier was automatically transferred to a lower-cost tier.

Automatic Tier Migration Mechanism

Smart Tier automatically moves data between three access tiers: Hot, Cool, and Cold. By default, new data is placed in the Hot tier, and objects that have not been accessed for 30 days are moved to the Cool tier, while those that have been inactive for 90 days are transferred to the Cold tier.

# Azure CLI command example to enable Smart Tier
az storage account update \
  --name mystorageaccount \
  --resource-group myresourcegroup \
  --access-tier Smart

Accessed objects are automatically moved back to the Hot tier, and the tiering cycle resumes. This automatic migration enables significant cost reduction without the need for manual lifecycle management rules. (Source: azure.microsoft.com)

Prerequisites and Setup Procedure for Enabling Smart Tier

To use Smart Tier, an account that supports Zone Redundant Storage (ZRS, GZRS, RA-GZRS) is required. It is available for both flat namespaces and hierarchical namespaces (ADLS).

Setup procedure:

  1. Register the “Smart Tier (account level)” feature in the Azure portal’s preview features blade.
  2. Select Smart Tier in the storage account’s default access tier settings.
# PowerShell setup example
Set-AzStorageAccount -ResourceGroupName "myResourceGroup" `
                     -Name "mystorageaccount" `
                     -AccessTier "Smart"

Enabling Smart Tier on an existing storage account will migrate all blobs without an explicitly set access tier to Smart Tier. (Source: learn.microsoft.com)

Pricing Model and Limitations

Smart Tier incurs a monitoring fee of $0.04 (USD) per 10,000 operations for monitoring operations. However, there is no charge for tier migration, early deletion, or capacity rehydration, simplifying the billing model.

Important limitations:

  • Redundancy conversion to non-zone redundant (LRS or GRS) accounts is not supported.
  • If a GZRS account fails over, it must be converted to zone redundancy within 60 days to continue supporting Smart Tier.
  • Legacy account types, such as Standard general-purpose v1 (GPv1), are not supported.

Objects with an explicitly set tier cannot be reverted to Smart Tier. (Source: learn.microsoft.com)

Summary

  • Enabling Smart Tier reduces the operational burden of data access pattern analysis and manual lifecycle management.
  • Setting the access tier to Smart using Azure CLI or PowerShell allows for immediate automatic optimization of existing data.
  • With a monitoring fee of $0.04 per 10,000 operations, Smart Tier can reduce storage costs by up to 50% while avoiding charges for tier migration and early deletion.
  • In analytical workloads like Azure Data Explorer, Smart Tier can automatically optimize the cost of infrequently used data while maintaining fast access to hot data.